JP7419889B2 - Communication control equipment and control method for communication control equipment - Google Patents

Description

The present invention relates to a communication control device, etc. that transfers data from a main memory to a transmission buffer according to a read descriptor, and transmits the data transferred to the transmission buffer.

Conventionally, various attempts have been known to distribute the load on processors of industrial control devices such as PLCs (Programmable Logic Controllers; hereinafter also referred to as PLCs). For example, Patent Document 1 listed below includes a processor consisting of a plurality of cores, a plurality of queues, and a plurality of communication ports, each queue is associated with each core, and the processing results in each core are transmitted to each core. Disclosed is a controller that stores data in each queue corresponding to a queue. In the controller of Patent Document 1, the same number of queues as the number of cores are provided, and the same number of communication ports as the number of queues are provided, so that each queue corresponding to each core can output processing results in each core, etc. We are trying to reduce the burden on the processor by controlling the

Japanese Patent Application Publication No. 2008-134775

However, in the conventional technology as described above, since transmission queues are divided for each network segment, there is a problem that as the number of network segments increases, a plurality of transmission queues are required, making it difficult to implement. That is, there is a limit to the number of transmission queues that can be increased, taking into account the amount of semiconductors in network interface cards (NICs), the amount of gates used in field-programmable gate arrays (FPGAs), and the like.

One aspect of the present invention aims to realize a communication control device that can reduce the processing load on software (processor) while suppressing the implementation size.

In order to solve the above problems, a communication control device according to one aspect of the present invention provides a communication control device that transfers data from a main memory to a transmission buffer according to a read descriptor, and transmits the data transferred to the transmission buffer. a selection unit that is a control device and selects a descriptor to be read from among the plurality of descriptors based on at least one of a scheduled transmission time and an execution priority defined in each of the plurality of descriptors; and a reading section that reads the descriptor selected by the selection section.

According to the above configuration, the communication control device selects a descriptor to read from among the plurality of descriptors based on at least one of the scheduled transmission time and the execution priority defined in each of the plurality of descriptors. select. Then, the communication control device reads the selected descriptor and transfers the data from the main memory to the transmission buffer according to the read descriptor. That is, the communication control device selects one descriptor to read from among the plurality of descriptors based on at least one of the scheduled transmission time and execution priority of each of the plurality of descriptors.

Therefore, the communication control device does not need to include a plurality of transmission queues each including a DMAC (Direct Memory Access Controller) and a transmission buffer, and the implementation size can be reduced.

Furthermore, the communication control device controls the output of processing results by software (processor), specifically, the transmission order of the data, by controlling the reading order of the plurality of descriptors. In other words, the software can treat the communication control device as one piece of hardware that includes a plurality of transmission queues that manage the "transmission order and actual transmission time (actual transmission time) of transmission data." Therefore, the communication control device can reduce the processing load of software related to output control of processing results (for example, management of "transmission order and actual transmission time of transmission data").

Therefore, the communication control device has the effect of being able to reduce the processing load of software while suppressing the implementation size.

Regarding the communication control device according to one aspect of the present invention, when the execution priority of a certain descriptor among the plurality of descriptors is higher than the execution priority of another descriptor, the selection unit (A) Transfer time required to transfer data corresponding to the certain descriptor from the main memory to the transmission buffer and transfer data corresponding to the other descriptor from the main memory to the transmission buffer at the current time (B) the scheduled transmission time of the certain descriptor is compared, and the scheduled transmission time of the certain descriptor is determined to be equal to the scheduled total time. If the scheduled transmission time of the certain descriptor is before the scheduled total time, the other descriptor is selected in preference to the other descriptor. A certain descriptor may be selected.

According to the above configuration, when the execution priority of the certain transmission descriptor is higher than the execution priority of the other descriptor, the communication control device determines the scheduled total time and the transmission schedule of the certain descriptor. Compare with the time. If the scheduled transmission time of the certain descriptor is later than the scheduled total time, the communication control device selects the other descriptor in preference to the certain descriptor. Further, if the scheduled transmission time of the certain descriptor is before the scheduled total time, the communication control device selects the certain descriptor in preference to the other descriptor.

Here, if a descriptor to be read is selected based only on the execution priority specified in each of the plurality of descriptors, the descriptor with a lower execution priority is always read after the descriptor with a higher execution priority. It will be.

However, if the scheduled transmission time of the other descriptor whose execution priority is lower than that of the certain descriptor is sufficiently earlier than the scheduled transmission time of the certain descriptor, the reading order of the descriptors may be determined only according to the execution priority. is not necessarily appropriate.

For example, even after the transmission data corresponding to the other descriptor has been transferred to the main memory, the transmission data corresponding to the certain transmission descriptor may be transferred before the scheduled transmission time of the certain transmission descriptor. In some cases, the data can be transferred to the main memory. In such a case, the certain descriptor may be read after reading (executing) the other descriptor; that is, the other descriptor should be read before the certain transmission descriptor.

Furthermore, if a descriptor to be read is selected based only on the scheduled transmission time specified in each of the plurality of descriptors, a descriptor with a later scheduled transmission time is always read after a descriptor with an earlier scheduled transmission time. It turns out.

However, if the scheduled transmission time of the other descriptor, which has a lower execution priority than the certain descriptor, is immediately before the scheduled transmission time of the certain descriptor, the reading order of the descriptors is determined only according to the scheduled transmission time. is not necessarily appropriate.

For example, after the transmission data corresponding to the other descriptor is transferred to the main memory, the transmission data corresponding to the certain transmission descriptor is transferred to the main memory before the scheduled transmission time of the certain transmission descriptor. It may not be possible to transfer to. In such a case, the certain descriptor must be read before reading (executing) the other descriptor, that is, the certain descriptor should be read before the other send descriptor. be.

The communication control device compensates for the above-mentioned deficiencies in determining the descriptor reading order based only on the execution priority and determining the descriptor reading order based only on the scheduled transmission time. That is, when the execution priority of a certain descriptor among the plurality of descriptors is higher than the execution priority of another descriptor, the communication control device determines the scheduled total time and the transmission of the certain descriptor. Compare with the scheduled time. Then, the communication control device selects a descriptor to be read based on a comparison result between the scheduled total time and the scheduled transmission time of the certain descriptor.

Therefore, the communication control device has the effect of being able to appropriately select a descriptor to be read, compared to a method of selecting a descriptor to be read based only on either the execution priority or the scheduled transmission time.

In the communication control device according to one aspect of the present invention, a determination time is set in advance, and the reading unit reads the descriptor after the determination time has elapsed from the scheduled transmission time of the descriptor. good.

According to the above configuration, the communication control device reads the descriptor after the determination time has elapsed from the scheduled transmission time of the descriptor.

Here, after reading a certain descriptor, if another descriptor is generated whose scheduled transmission time is closer to the current time than the scheduled transmission time of the certain descriptor, the following problem occurs. That is, a problem arises in that the data corresponding to the certain descriptor becomes a failure and the data corresponding to the other descriptor cannot be transmitted at the scheduled transmission time of the other descriptor.

This is because the data stored in the transmission buffer is transmitted in the order in which it was stored. In other words, if the data corresponding to the certain descriptor is stored before the data corresponding to the another descriptor, the data corresponding to the other descriptor must be stored after the data corresponding to the certain descriptor is transmitted. No data is sent. The data corresponding to the certain descriptor is not transmitted until the scheduled transmission time of the certain descriptor. However, since the scheduled transmission time of the certain descriptor is later than the scheduled transmission time of the other descriptor, it is impossible to transmit the data corresponding to the other descriptor at the scheduled transmission time of the other descriptor. Can not.

Therefore, the communication control device suppresses the possibility that the above-mentioned problem will occur by reading the descriptor after the determination time has elapsed from the scheduled transmission time of the descriptor. That is, the communication control device is configured to read the certain descriptor before reading the other descriptor whose scheduled transmission time is closer to the current time than the scheduled transmission time of the certain descriptor. Adjust the read time of a certain descriptor. Specifically, the communication control device reads the certain descriptor after the determination time has elapsed from the scheduled transmission time of the certain descriptor.

Therefore, the communication control device can prevent the certain descriptor from being read before reading the other descriptor whose scheduled transmission time is closer to the current time than the scheduled transmission time of the certain descriptor. It has the effect of

In the communication control device according to one aspect of the present invention, the transmission buffer includes a normal transmission buffer in which the data corresponding to the descriptor is stored, and a normal transmission buffer in which the data is stored in the order of the descriptors read by the reading unit. A descriptor read by the reading unit after the selection unit selects the descriptor corresponding to the data stored in the normal transmission buffer and before the data stored in the normal transmission buffer is transmitted, A special transmission buffer may be included in which the data corresponding to the descriptor having a higher execution priority than the descriptor corresponding to the data stored in the normal transmission buffer is stored.

According to the above configuration, the communication control device includes the transmission buffer including the normal transmission buffer and the special transmission buffer. Then, the communication control device normally stores data corresponding to the read descriptors in the normal transmission buffer in the order of the read descriptors.

The communication control device transmits new data during the period from "selecting the descriptor corresponding to the data stored in the normal transmission buffer to transmitting the data stored in the normal transmission buffer". When a descriptor is read, the following judgments are performed. That is, the communication control device determines whether the execution priority of the new descriptor is higher than the execution priority of the descriptor corresponding to the data stored in the normal transmission buffer.

If the execution priority of the new descriptor is higher, the communication control device stores data corresponding to the new descriptor in the special transmission buffer. If the execution priorities of the new descriptor are lower or the execution priorities are the same, the communication control device stores data corresponding to the new descriptor in the normal transmission buffer.

Here, after the selection unit selects a certain descriptor and until data corresponding to the certain descriptor is transmitted, another descriptor having a higher execution priority than the certain descriptor is read. may be read. In such a case, if there is only one transmission buffer, the data corresponding to the other descriptor must be stored in the only one transmission buffer after the data corresponding to the certain descriptor. . As a result, it becomes impossible to transmit data corresponding to the other descriptor before data corresponding to the certain descriptor.

On the other hand, the communication control device includes the transmission buffer including the normal transmission buffer and the special transmission buffer. Then, as described above, when new data that should be transmitted with priority over data stored in the normal transmission buffer is generated, the communication control device stores such data in the special transmission buffer.

Therefore, the communication control device prioritizes data that is generated between selecting the certain descriptor and transmitting the data corresponding to the certain descriptor and should be transmitted with priority over data corresponding to the certain descriptor. This has the effect of allowing priority transmission.

In order to solve the above problems, a control method according to one aspect of the present invention provides communication control that transfers data from a main memory to a transmission buffer according to a read descriptor, and transmits the data transferred to the transmission buffer. A method for controlling a device, the method comprising: selecting a descriptor to read from a plurality of descriptors based on at least one of a scheduled transmission time and an execution priority defined in each of the plurality of descriptors; , a reading step of reading the descriptor selected in the selection step.

According to the above configuration, the control method selects a descriptor to be read from among the plurality of descriptors based on at least one of a scheduled transmission time and an execution priority defined in each of the plurality of descriptors. do. The control method reads the selected descriptor and transfers the data from the main memory to the transmission buffer according to the read descriptor. That is, the control method selects one descriptor to be read from among the plurality of descriptors based on at least one of the scheduled transmission time and execution priority of each of the plurality of descriptors.

Therefore, the communication control device that executes the control method does not need to include multiple transmission queues, each including a DMAC and a transmission buffer, and the implementation size of the communication control device that executes the control method can be reduced. .

Furthermore, the control method controls the output of processing results by software (processor), specifically, the transmission order of the data, by controlling the reading order of the plurality of descriptors. In other words, the software can treat the communication control device as one piece of hardware that includes a plurality of transmission queues that manage "the transmission order and actual transmission time of transmission data." Therefore, the communication control device can reduce the processing load of software related to output control of processing results (for example, management of "transmission order and actual transmission time of transmission data").

Therefore, the control method has the effect of being able to reduce the processing load of software while suppressing the implementation size of a communication control device that executes the control method.

According to one aspect of the present invention, it is possible to reduce the processing load on software (processor) while suppressing the implementation size.

1 is a diagram showing a main part configuration of a PLC including a communication controller according to Embodiment 1 of the present invention. 2 is a diagram showing an overview of a control system including the PLC of FIG. 1. FIG. FIG. 2 is a flow diagram illustrating an overview of processing executed by the communication controller according to Embodiment 1 of the present invention. FIG. 6 is a diagram illustrating a situation that occurs when a descriptor to be read first is selected based only on priority in case 1; FIG. 6 is a diagram illustrating a situation that occurs when a descriptor to be read first is selected based only on the transmission time in case 2; FIG. 3 is a flow diagram showing an example of a selection process executed by the communication controller according to Embodiment 1 of the present invention in consideration of priority and transmission time. 7 is a diagram illustrating descriptors selected by the communication controller according to Embodiment 1 of the present invention by executing the flow illustrated in FIG. 6. FIG. 7 is a diagram illustrating a specific processing example when the flow illustrated in FIG. 6 is executed for case 1. FIG. 7 is a diagram illustrating a specific example of processing when the flow illustrated in FIG. 6 is executed for case 2. FIG. 3 is a table in which information used by the communication controller according to Embodiment 1 of the present invention when calculating the transfer time of certain transmission data is organized. FIG. 7 is a diagram illustrating a situation that occurs when no determination time is provided in case 3. 7 is a diagram illustrating a specific processing example that is realized when a determination time is provided in the communication controller according to the first embodiment of the present invention for case 3. FIG. FIG. 2 is a flow diagram illustrating an example of processing executed by a CPU and a requester. FIG. 3 is a flow diagram showing an example of processing executed by a descriptor execution management unit, a BUF management unit, and the like. FIG. 15 is a flow diagram illustrating an example of the selection process illustrated in FIG. 14(A). 16 is a flow diagram illustrating an example of the update processing illustrated in FIG. 15 when the priority of the target descriptor is the same as the current priority and when the former is higher than the latter; FIG. 16 is a flow diagram illustrating an example of the update process illustrated in FIG. 15 when the priority of the target descriptor is lower than the current priority. FIG.

[Embodiment 1]
DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment (hereinafter also referred to as "this embodiment") according to one aspect of the present invention will be described below based on the drawings. In addition, the same reference numerals are attached to the same or corresponding parts in the drawings, and the description thereof will not be repeated. In this embodiment, a communication controller 10 provided in a PLC (Programmable Logic Controller) 1 that controls controlled objects such as machines and equipment will be described as a typical example of communication control equipment.

In the following explanation, "n" indicates an integer greater than or equal to "1", and "buffer" is sometimes abbreviated as "BUF", and "descriptor memory" that stores transmission descriptors is sometimes abbreviated as TX. . For example, the first buffer 162(0) is abbreviated as "BUF0," the second buffer 162(1) is abbreviated as "BUF1," and the nth buffer 162(n-1) is abbreviated as "BUFn-1." Sometimes. If there is no particular need to distinguish between the first buffer 162(0), the second buffer 162(1), and the n-th buffer 162(n-1), they may simply be referred to as "buffer 162" or "BUF". There is.

Similarly, the first descriptor memory 14(0) is abbreviated as "TX0", the second descriptor memory 14(1) is abbreviated as "TX1", and the n-th descriptor memory 14(n-1) is abbreviated as "TXn-1". ” is sometimes abbreviated as “. If there is no particular need to distinguish between the first descriptor memory 14 (0), the second descriptor memory 14 (1), and the n-th descriptor memory 14 (n-1), simply "descriptor memory 14" or "TX ”.

Furthermore, if there is no particular need to distinguish between the first requester 15(0), the second requester 15(1), and the n-th requester 15(n-1), they may be simply referred to as "requester 15." .

§1. Application Example To facilitate understanding of the communication controller 10 (communication control device) according to one aspect of the present invention, first, an example of a scene to which the present invention is applied will be described, specifically, a PLC 1 including the communication controller 10. An overview of the control system 0 including the following will be described using FIG. 2.

(Overview of control system)
FIG. 2 is a diagram showing an overview of the control system 0. As shown in FIG. The control system 0 includes a PLC 1, a network hub 2, and networks 3(1) and 3(2) each connected to the PLC 1 via the network hub 2. Hereinafter, if there is no need to particularly distinguish between network 3(1) and network 3(2), they may be simply referred to as "network 3." Network 3 includes one or more network devices.

In the control system 0 illustrated in FIG. 2, a plurality of networks 3 are connected to the PLC 1 via the network hub 2. A giga band may be used for communication in the control system 0.

The PLC 1 is a control device that controls the entire control system 0, and the network hub 2 is a network hub or a network switch that manages communication between the PLC 1 and a plurality of networks 3. In the control system 0 shown in FIG. 2, a plurality of networks 3, for example, networks 3(1) and 3(2), Existing.

Here, both networks 3(1) and 3(2) may be control networks, or in other words, all networks 3 that communicate with PLC 1 may be control networks. Further, either one of the networks 3(1) and 3(2) may be a control network and the other may be a data network. In other words, for the network 3 that communicates with the PLC 1, the control network and the data network may be They may be mixed.

For example, if the network 3 is a control network, the PLC 1 is a control device that controls input equipment and output equipment in the production equipment, and the network device is, for example, an input equipment and output equipment in the production equipment. be. The PLC 1 and the network device communicate cyclically via the network 3 to send and receive IN data and OUT data (hereinafter referred to as "IO data"), and the PLC 1 controls the entire production equipment. . That is, when the network 3 is a control network, the control system 0 can be regarded as a master-slave control system in which the PLC 1 is a master device (a master device that manages data transmission) and the network devices are slave devices.

When the network 3 is a control network, the network 3 may be compliant with an industrial Ethernet standard such as an EtherCAT (Ethernet for Control Automation Technology) standard. If the network 3 is a control network, the network 3 may be compliant with the EtherNet/IP (registered trademark) standard.

Below, an example will be described in which communication between the PLC 1 and the network device in FIG. 2 (hereinafter also referred to as "network communication") conforms to the Ethernet standard. Further, it is assumed that the CPU 30 and the communication controller 10 are communicably connected via PCIe (Peripheral Component Interconnect Express).

Although FIG. 2 illustrates a control system 0 in which a plurality of networks 3 are connected to a PLC 1 via a network hub 2, in the control system 0, a plurality of networks 3 are connected to a PLC 1 via a network hub 2. It is not necessary to connect the In the control system 0, one network 3 (in particular, one control network) may be connected to the PLC 1 without going through the network hub 2. For example, in the control system 0, which is a master-slave control system, the PLC 1, which is a master device, and one or more network devices, each of which is a slave device, may be communicably connected in a single stroke format.

(Summary of processing executed by the communication controller according to this embodiment)
In order to facilitate understanding of the communication controller 10, which will be described in detail below using FIG. 1 and the like, the processes executed by the communication controller 10 will be summarized as follows.

That is, when the communication controller 10 receives multiple transmission requests (that is, execution requests for multiple transmission descriptors) from software (that is, the CPU 30) almost simultaneously, the descriptor execution management unit 13 of the communication controller 10 executes the selection process. .

In the selection process, first, the descriptor execution management unit 13 (in particular, the selection unit 131) determines the "transmission time TT" and "priority P specified by software" for each of the plurality of transmission descriptors (descriptors) to be executed. get. Then, the descriptor execution management unit 13 uses the acquired "transmission time TT and priority P of each of the plurality of descriptors" to select a descriptor to be executed, that is, a descriptor to be read. Although details will be described later, the descriptor execution management unit 13 may use "the data size (that is, the data transfer size) of each of a plurality of descriptors" when selecting a descriptor to read.

Here, in order to reduce the processing load on the CPU, a configuration is known in which the "transmission order and actual transmission time (actual transmission time RTT) of transmission data" is managed by a NIC etc. configured with a hardware logic circuit. It is being The "actual transmission time RTT" is the time at which the transmission data is actually transmitted, and the transmission that matches the actual transmission time RTT with the transmission time TT is also referred to as "time transmission."

In an example of a NIC that manages "transmission order and actual transmission time RTT of transmission data," the transmission queue that manages "transmission order and actual transmission time RTT of transmission data" is a DMAC (Direct Memory Access Controller). and a transmission BUF. In an example of such a NIC, a ``transmission queue equipped with a DMAC and a transmission BUF'' is provided for each communication network that should manage ``the transmission order and actual transmission time RTT of transmission data.'' .

However, if you try to set up a ``transmission queue equipped with a DMAC and a transmission BUF'' in the NIC for each communication network that should manage the ``transmission order and actual transmission time RTT of transmission data,'' the following problem will occur. . That is, as the number of communication networks to be managed as described above increases, the number of "transmission queues including DMAC and transmission BUF" also increases, resulting in an increase in the implementation size of the NIC.

On the other hand, the communication controller 10 does not need to have a plurality of "transmission queues including a DMAC and a transmission BUF" by executing the above-mentioned selection process (in particular, the selection process of a descriptor to be read).

For example, the communication controller 10 illustrated in FIG. 1 includes "two" buffers 162 for temporarily holding transmission data read from the main memory 20 before sending it. The number of buffers 162 provided may be "one". In other words, since the communication controller 10 executes a plurality of descriptors to be executed one by one in a desired order, the communication controller 10 has "one" buffer 162 for temporarily holding transmission data. Just be prepared. However, by providing "two" or more buffers 162, if the communication controller 10 executes a certain descriptor and then executes another descriptor with a higher priority P, the communication controller 10 can respond to that other descriptor. Data can be sent with priority. The configuration in which the communication controller 10 includes "two" or more buffers 162 will be described in detail later.

Further, as illustrated in FIG. 1, the communication controller 10 can execute a plurality of descriptors to be executed one by one in a desired order, thereby realizing data exchange between the main memory 20 and the buffer 162. It suffices to have "one" DMAC 12 to do this.

Therefore, the communication controller 10 does not need to include a plurality of "transmission queues including a DMAC and a transmission BUF", so the implementation size can be reduced. In particular, even if the number of communication networks (networks 3) that have to manage the "transmission order and actual transmission time RTT of transmission data" increases, the communication controller 10 can suppress expansion of the implementation size.

Although details will be described later using FIG. 1, the communication controller 10 includes "one" transmission port 18 and "one" DMAC 12. The communication controller 10 includes a plurality of transmission queues for managing "the transmission order and actual transmission time RTT of transmission data" for "one" transmission port 18 and "one" DMAC 12. . Specifically, the communication controller 10 includes a plurality of descriptor memories 14 and a plurality of requesters 15, and a descriptor execution management unit 13 for executing a plurality of descriptors to be executed one by one in a desired order. We have one. The communication controller 10 includes a plurality of transmission queues that manage "transmission order and actual transmission time RTT of transmission data" by a plurality of descriptor memories 14, a plurality of requesters 15, and a descriptor execution management unit 13. Achieve the same effect as . Therefore, the communication controller 10 can manage the "transmission order and actual transmission time RTT of transmission data" in the same way as having a plurality of transmission queues while suppressing the implementation size.

For example, the communication controller 10 is configured with a hardware logic circuit such as an FPGA (Field-Programmable Gate Array) or an ASIC (Application Specific Integrated Circuit). In that case, the software (that is, the CPU 30) can treat the communication controller 10 as hardware that includes a plurality of transmission queues that manage "the transmission order and actual transmission time RTT of transmission data." Therefore, by configuring the communication controller 10 with a hardware logic circuit, the communication controller 10 that manages "the transmission order and actual transmission time RTT of transmission data" reduces the processing load on software (that is, the CPU 30). can do.

Therefore, the communication controller 10 can be organized as follows. That is, the communication controller 10 (communication control device) transfers data (transmission data) from the main memory 20 to the buffer 162 (transmission buffer) according to the read transmission descriptor, and performs communication control to transmit the data transferred to the buffer 162. It is a device.

The communication controller 10 includes a selection section 131 and a reading section 132. The selection unit 131 selects one of the plurality of transmission descriptors based on at least one of "transmission time TT (scheduled transmission time)" and "priority P (execution priority)" defined in each of the plurality of transmission descriptors. Select the send descriptor to read from among them. That is, the selection unit 131 selects the transmission descriptor to be executed from among the plurality of transmission descriptors based on "at least one of transmission time TT and priority P" defined in each of the plurality of transmission descriptors. . Further, the reading unit 132 reads the transmission descriptor selected by the selection unit 131, that is, executes the transmission descriptor selected by the selection unit 131.

According to the above configuration, the communication controller 10 selects a descriptor to read from among the plurality of transmission descriptors based on at least one of the transmission time TT and the priority P defined in each of the plurality of transmission descriptors. do. The communication controller 10 then reads the selected transmission descriptor and transfers the transmission data from the main memory 20 to the buffer 162 according to the read transmission descriptor. That is, the communication controller 10 selects one descriptor to be read from among the plurality of transmission descriptors based on at least one of the transmission time TT and priority P of each of the plurality of transmission descriptors.

Therefore, the communication controller 10 does not need to include a plurality of transmission queues, each including a DMAC and a transmission buffer, and the implementation size can be reduced.

In addition, the communication controller 10 controls the output of processing results by software (processor, that is, the CPU 30) by controlling the reading order of a plurality of transmission descriptors. transmission time RTT". That is, the software can treat the communication controller 10 as one piece of hardware that includes a plurality of transmission queues that manage "the transmission order and actual transmission time RTT of transmission data." Therefore, the communication controller 10 can reduce the processing load of software related to output control of processing results (for example, management of "transmission order and actual transmission time RTT of transmission data").

Therefore, the communication controller 10 has the effect of being able to reduce the processing load of software while suppressing the implementation size.

In the communication controller 10, the buffers 162 are roughly divided into normal transmission buffers and special transmission buffers. Normally, data corresponding to transmission descriptors is stored in the transmission buffer in the order of transmission descriptors read by the reading unit 132. The special transmission buffer stores data corresponding to "a descriptor that satisfies both the following two conditions". Condition 1 is that the reading unit 132 reads a descriptor between the time the selection unit 131 selects the transmission descriptor corresponding to the data stored in the normal transmission buffer and the time that data is transmitted. It is "to be". Condition 2 is "priority P is higher than the transmission descriptor corresponding to data normally stored in the transmission buffer".

At least one of the first buffer 162 (0), second buffer 162 (1), ..., n-th buffer 162 (n-1) is used as a special transmission buffer, and the other buffers 162 are used for normal transmission. It can also be used as a buffer.

According to the above configuration, the communication controller 10 includes a buffer 162 including the normal transmission buffer and the special transmission buffer. Then, the communication controller 10 normally stores data corresponding to the read transmission descriptors in the normal transmission buffer in the order of the read transmission descriptors.

The communication controller 10 reads a new descriptor between "selecting the transmission descriptor corresponding to the data stored in the normal transmission buffer and before transmitting the data stored in the normal transmission buffer". and executes the following judgment. That is, the communication controller 10 determines whether the priority P of the new descriptor is higher than the priority P of the transmission descriptor corresponding to the data stored in the normal transmission buffer.

If the new descriptor has a higher priority P, the communication controller 10 stores data corresponding to the new descriptor in the special transmission buffer. On the other hand, if the priority P of the new descriptor is lower, or if both priorities P are the same, the communication controller 10 stores the data corresponding to the new descriptor in the normal transmission buffer. do.

Here, after the selection unit 131 selects a certain transmission descriptor until the data corresponding to that certain transmission descriptor is transmitted, another descriptor having a higher priority P than that certain transmission descriptor is selected. There is a possibility that the reading unit 132 reads it. In such a case, if there was only one send buffer, the data corresponding to that other descriptor would have to be stored in the only send buffer after the data corresponding to that certain send descriptor. do not have. As a result, it becomes impossible to transmit data corresponding to that other descriptor before data corresponding to that certain transmission descriptor.

On the other hand, the communication controller 10 includes a buffer 162 including the normal transmission buffer and the special transmission buffer. Then, as described above, when new data that should be transmitted with priority over data stored in the normal transmission buffer is generated, the communication controller 10 stores such data in the special transmission buffer.

Therefore, the communication controller 10 prioritizes data that should be transmitted with priority over data corresponding to a certain transmission descriptor that has occurred after selecting a certain transmission descriptor and before transmitting data corresponding to that certain transmission descriptor. It has the effect of being able to send data.

§2. Configuration Example Next, details of the communication controller 10 and the PLC 1 including the communication controller 10, which have been outlined so far, will be explained using FIG.

FIG. 1 is a diagram showing an example of the configuration of the PLC 1. As shown in FIG. As illustrated in FIG. 1, the PLC 1 includes a communication controller 10, a main memory 20, and a CPU 30 as a hardware configuration. The PLC 1 may further include a non-volatile memory (not shown), a USB connector for connecting an external device and the PLC 1, and the like. The communication controller 10, main memory 20, CPU 30, and nonvolatile memory are each coupled via various buses (internal buses).

The CPU 30 is typically configured according to a general-purpose computer architecture, and sequentially interprets and executes instruction codes according to an internal clock. The hardware configuration of the CPU 30 includes one or more CPU cores and a network control unit.
The CPU 30 executes various arithmetic processes and stores data generated as the execution results in the main memory 20 as transmission data. Further, the CPU 30 stores descriptor data in the main memory 20 that defines the priority P, transmission time TT, address in the main memory 20, data size, etc. of the data stored in the main memory 20 as transmission data. Store. Descriptor data that defines the priority P of transmission data, transmission time TT, address in the main memory 20, data size, etc. is sometimes abbreviated as a "transmission descriptor" or simply "descriptor."

The "transmission time TT" of the transmission data is given by the CPU 30 and indicates the time at which the communication controller 10 transmits the transmission data to the network 3. In other words, the transmission data should be transmitted to the network 3. Indicates the scheduled transmission time. Furthermore, the "priority P" of the transmission data is given by the CPU 30 and indicates the degree of necessity to "transmit the transmission data at the 'transmission time TT'". This indicates the high level of need to maintain and periodically transmit data to network 3.

Here, in general, an industrial controller such as the PLC 1 and a device (for example, the "network device" in FIG. 2) exchange data at regular intervals. In the control system 0, one or more data exchange cycles and communication priority CP of the unit group may be set for a unit group including one or more network devices.

The communication priority CP and the priority P may be associated with each other. Furthermore, the fact that the communication priority CP of a certain unit group (e.g., unit group U1) is higher than the communication priority CP of another unit group (e.g., unit group U2) means that the communication cycle of that certain unit group may mean that the need to maintain the unit is higher than that of another group of units. Furthermore, the fact that the communication priority CP of a certain unit group (e.g., unit group U1) is higher than the communication priority CP of another unit group (e.g., unit group U2) means that the communication cycle of that certain unit group may also mean that the communication cycle is faster (shorter) than the communication cycle of that other unit group.

For example, "periodic communication that the PLC 1 (particularly the communication controller 10) performs with a certain network device" is more important than "periodic communication that the PLC 1 performs with another network device". There are times when it is necessary to maintain communication cycles. In such a case, the communication priority CP of "periodic communication performed with that certain network device" is higher than the communication priority CP of "periodic communication performed with that certain network device". Higher priority than CP.

Furthermore, "periodic communication that the PLC 1 (particularly the communication controller 10) performs with a certain network device" is more important than "periodic communication that the PLC 1 performs with another network device". The communication cycle may be short (fast). In such a case, the communication priority CP of "periodic communication performed with that certain network device" is higher than the communication priority CP of "periodic communication performed with that certain network device". Higher priority than CP.

If the communication priority CP of "periodic communication performed with a certain network device" is higher than the communication priority CP of "periodic communication performed with another network device", the CPU 30 assigns priority P to transmission data as follows. That is, the CPU 30 assigns a higher priority P to "transmission data destined for that certain network device" than priority P given to "transmission data destined for that other network device."

The main memory 20 is a storage means of the PLC 1, and stores, for example, data (transmission data) that the PLC 1 (in particular, the communication controller 10) transmits to the network 3. The main memory 20 is a volatile storage area (RAM), and in addition to storing transmission data "generated by various calculation processes by the CPU 30 and transmitted to the network 3", the main memory 20 is a volatile storage area (RAM). Holds various programs to be executed. The main memory 20 is also used as a working memory when the CPU 30 executes various programs. As such main memory 20, for example, DRAM (Dynamic Random Access Memory), SRAM (Static Random Access Memory), etc. can be used.

The main memory 20 illustrated in FIG. 1 stores transmission data as well as descriptor data (transmission descriptor) corresponding to the transmission data. The transmission descriptor includes information indicating the transmission time TT, priority P, data size, etc. of the corresponding transmission data.

The PLC 1 may include a nonvolatile memory that holds data such as various programs and parameters in a nonvolatile manner. These data stored in the nonvolatile memory are copied to the main memory 20 so that the CPU 30 can access them, if necessary. A semiconductor memory such as a flash memory can be used as such nonvolatile memory. Alternatively, a magnetic recording medium such as a hard disk drive, an optical recording medium such as a DVD-RAM (Digital Versatile Disk Random Access Memory), etc. can also be used.

The communication controller 10 is a communication control device that transmits data (transmission data) stored in the main memory 20 to the network 3, and is realized as, for example, a NIC (Network Interface Card). The communication controller 10 is typically configured with a hardware logic circuit such as an FPGA (Field-Programmable Gate Array) or an ASIC (Application Specific Integrated Circuit). The communication controller 10 is configured to be able to send and receive data to and from each of the main memory 20 and the CPU 30.

The communication controller 10 is connected to the network 3 via the transmission port 18, and controls the exchange of data with the network 3, and in particular controls the transmission of transmission data. time RTT”. The communication controller 10 provides, for example, physical layer and data link layer functions in the network 3. That is, the communication controller 10 controls the transmission of transmission data and the reception of reception data in accordance with the standards that the network 3 complies with. Specifically, the communication controller 10 transfers the data (transmission data) stored in the main memory 20 to the buffer 162 in its own device, and transfers the transmission data stored in the buffer 162 to the data connected to the network 3. network device.

The communication controller 10 transmits the transmission data according to the contents specified in the transmission descriptor, and transmits the transmission data corresponding to the transmission descriptor at the transmission time TT specified in the transmission descriptor, for example. The communication controller 10 transmitting the transmission data at the transmission time TT set for the transmission data (that is, the transmission time TT specified in the transmission descriptor corresponding to the transmission data) is also called "time transmission". to be called.

Here, the communication controller 10 controls the transmission order of the plurality of transmission data by the order in which the plurality of transmission data is stored in the buffer 162, and specifically, the transmission order of the plurality of transmission data is controlled by the order in which the plurality of transmission data are stored in the buffer 162. Control the reading order (execution order). In particular, the communication controller 10 selects a transmission descriptor to be read preferentially based on at least one of the transmission time TT and the priority P defined in each of the plurality of transmission descriptors.

Although details will be described later, the PLC 1 uses the communication controller 10, which is configured not by the CPU 30 but by a hardware logic circuit, to determine the transmission order and actual transmission of data (transmission data) stored in the main memory 20 to the network 3. Controls time RTT. Therefore, the PLC 1 can control the transmission order of transmission data to the network 3 and the actual transmission time RTT by the communication controller 10 configured with a hardware logic circuit without increasing the processing load of the CPU 30. It has the effect of

The communication controller 10 illustrated in FIG. 1 includes, as functional blocks, an IF 11, a DMAC 12, a descriptor execution management unit 13, two or more descriptor memories 14, two or more requesters 15, a BUF management unit 16, an arbitration unit 17, and A transmission port 18 is provided.

The IF 11 is an interface through which the communication controller 10 (particularly the DMAC 12) communicates with each of the main memory 20 and the CPU 30.

DMAC 12 performs data exchange between main memory 20 and each of descriptor memory 14 and buffer 162. For example, the DMAC 12 reads descriptor data (transmission descriptor) set in the main memory 20 by the CPU 30 and stores it in the descriptor memory 14.

Further, the DMAC 12 transfers the transmission data from the main memory 20 to the buffer 162 according to the contents specified in the transmission descriptor, that is, acquires the data stored in the main memory 20 and transfers the acquired data to the buffer. 162. For example, the DMAC 12 acquires from the main memory 20 the transmission data specified by the "address of the main memory 20" and "data size of the transmission data" defined in the transmission descriptor. The DMAC 12 transfers the transmission data corresponding to the transmission descriptor to the buffer 162 together with the "transmission time TT" defined in the transmission descriptor.

The DMAC 12 transfers the transmission data from the main memory 20 to the buffer 162 according to "the transmission descriptor stored in the descriptor memory 14 and read (executed) by the descriptor execution management unit 13". do.

When receiving a transmission request from the CPU 30, the descriptor execution management unit 13 transfers the transmission data from the main memory 20 to the buffer 162 in accordance with the transmission request. Specifically, when the descriptor execution management unit 13 is notified by the requester 15 that "there is a transmission descriptor to be executed (read)", the descriptor execution management unit 13 refers to the descriptor memory 14 and reads (executes) the transmission descriptor. ). Then, the descriptor execution management unit 13 sets the contents defined in the read transmission descriptor in the DMAC 12, and causes the DMAC 12 to transfer the transmission data from the main memory 20 to the buffer 162 according to the read transmission descriptor. The descriptor execution management section 13 includes a selection section 131 and a reading section 132.

When the selection unit 131 is notified by the requester 15 that "there is a transmission descriptor to be executed (read)", the selection unit 131 refers to the descriptor memory 14 corresponding to the requester 15 and selects the transmission descriptor stored in the descriptor memory 14. Get the descriptor. For example, when the selection unit 131 is notified from the first requester 15(0) that "there is a transmission descriptor to be read", the selection unit 131 stores the transmission descriptor in the first descriptor memory 14(0) corresponding to the first requester 15(0). Get the send descriptor that is being sent. Similarly, when the selection unit 131 is notified that "there is a transmission descriptor to be read" from the n-th requester 15 (n-1), the selection unit 131 selects the n-th descriptor memory 14 corresponding to the n-th requester 15 (n-1). Obtain the transmission descriptor stored in (n-1).

In response to a notification from the requester 15 that there is a transmission descriptor to be read, the selection unit 131 acquires a transmission descriptor from the descriptor memory 14 corresponding to the requester 15, and notifies the reading unit 132 of the acquired transmission descriptor. do.

When the selection unit 131 is notified from each of the plurality of requesters 15 that "there is a transmission descriptor to be read" almost simultaneously, the selection unit 131 determines the order of the transmission descriptors to be read (executed), that is, selects the transmission descriptor to be read preferentially. Select one by one. Then, the selection unit 131 notifies the reading unit 132 of the selected transmission descriptor.

Specifically, when the selection unit 131 is notified from each of the plurality of requesters 15 substantially simultaneously that "there is a transmission descriptor to be read", the selection unit 131 refers to the descriptor memory 14 corresponding to each of the plurality of requesters 15. Then, the selection unit 131 acquires the transmission descriptor stored in each of the plurality of descriptor memories 14 "each corresponding to each of the plurality of requesters 15".

The selection unit 131 acquires "at least one of the transmission time TT and the priority P" of each of the plurality of transmission descriptors "each stored in each of the plurality of descriptor memories 14". Then, the selection unit 131 determines the reading order of the plurality of transmission descriptors based on "at least one of the transmission time TT and priority P" of each of the plurality of transmission descriptors. Determine the execution order. Specifically, the selection unit 131 selects one of the plurality of transmission descriptors preferentially (that is, sooner) based on "at least one of the transmission time TT and priority P" of each of the plurality of transmission descriptors. ) Select the transmit descriptors to read one by one.

For example, when the selection unit 131 is notified from each of the first requester 15(0) and the second requester 15(1) substantially simultaneously that "there is a transmission descriptor to be read", the selection unit 131 executes the following process. . That is, the selection unit 131 refers to the first descriptor memory 14(0) corresponding to the first requester 15(0), and selects the transmission descriptor (for example, descriptor A) stored in the first descriptor memory 14(0). ) to obtain. Similarly, the selection unit 131 refers to the second descriptor memory 14(1) corresponding to the second requester 15(1), and selects a transmission descriptor (for example, a descriptor) stored in the second descriptor memory 14(1). B) Obtain.

The selection unit 131 obtains "at least one of the transmission time TT and the priority P" of each of the descriptor A and the descriptor B. Then, the selection unit 131 determines the reading order of descriptors A and B based on "at least one of transmission time TT and priority P" of each of descriptors A and B.

Specifically, the selection unit 131 selects the transmission descriptor to be read first from descriptor A and descriptor B based on "at least one of transmission time TT and priority P" of each of descriptors A and B. . Then, the selection unit 131 notifies the reading unit 132 of the selected transmission descriptor. When the selection unit 131 selects descriptor A as the transmission descriptor to be read first from descriptor A and descriptor B, it notifies the reading unit 132 of descriptor A. Further, when selecting descriptor B as the transmission descriptor to be read first from descriptor A and descriptor B, the selection unit 131 notifies the reading unit 132 of descriptor B.

When the reading unit 132 is notified of the transmission descriptor from the selection unit 131, the reading unit 132 reads the notified transmission descriptor, that is, executes the transmission descriptor notified from the selection unit 131. The reading unit 132 sets the contents specified in the read transmission descriptor in the DMAC 12, that is, notifies the DMAC 12 of the contents specified in the read transmission descriptor. Then, the reading unit 132 causes the DMAC 12 to execute a transfer process according to the contents specified in the read transmission descriptor. In other words, the reading unit 132 causes the DMAC 12 to transfer the transmission data from the main memory 20 to the buffer 162 according to the read transmission descriptor. Have it transferred.

The descriptor memory 14 stores transmission descriptors (descriptor data) in a FIFO (first in, first out) format. When the CPU 30 completes setting (storing) descriptor data in the main memory 20 and issues a transmission request to the communication controller 10, the communication controller 10 reads the descriptor data from the main memory 20 and stores it in the descriptor memory 14. .

The requester 15 includes a request register, and when a transmission descriptor is stored in the corresponding descriptor memory 14, "1" is stored in the request register of the requester 15. While "1" is stored in the request register, the requester 15 continues to notify the descriptor execution management section 13 (in particular, the selection section 131) that "there is a transmission descriptor to be executed (read)."

Further, when the transmission descriptor stored in the corresponding descriptor memory 14 is read and the transfer of the data corresponding to the transmission descriptor to the buffer 162 is completed, "0" is stored in the request register of the requester 15. While “0” is stored in the request register, the requester 15 notifies the descriptor execution management unit 13 (in particular, the selection unit 131) that “there is no transmission descriptor to be executed” or that there is no transmission descriptor to be executed. ``There is a send descriptor that should be sent.''

For example, when descriptor A is stored in the first descriptor memory 14(0), "1" is stored in the request register of the first requester 15(0) corresponding to the first descriptor memory 14(0). Then, when descriptor A is read and the transfer of the data corresponding to descriptor A to the buffer 162 is completed, "0" is stored in the request register of the first descriptor memory 14(0).

Similarly, when descriptor B is stored in the second descriptor memory 14(1), "1" is stored in the request register of the second requester 15(1) corresponding to the second descriptor memory 14(1). . Then, when descriptor B is read and the transfer of the data corresponding to descriptor B to the buffer 162 is completed, "0" is stored in the request register of the second descriptor memory 14(1).

Requester 15 further includes a configuration register 151. The setting register 151 stores an “execution number” and an “execution number” that are notified from the CPU 30 to the communication controller 10. Details of the "number of executions" and "execution number" will be described later.

The BUF management unit 16 controls the transmission order and actual transmission time RTT of the transmission data, and specifically transmits the transmission data to the network 3 at the transmission time TT set for the transmission data, or , try to send. The BUF management section 16 includes a time specified transmission management section 161 and a buffer 162.

The time-specified transmission management unit 161 transmits the transmission data stored in the buffer 162 at the transmission time TT set for the transmission data, that is, the transmission specified by the transmission descriptor corresponding to the transmission data. Send at time TT. Specifically, when data (transmission data) is stored in the buffer 162, the time-specified transmission management unit 161 checks the transmission time TT defined in the transmission descriptor corresponding to the transmission data. Then, the time-specified transmission management unit 161 outputs a transmission request to the arbitration unit 17 when the current time CT reaches the confirmed transmission time TT. The time-specified transmission management unit 161 transmits the transmission data to the network 3 if access permission is granted as a response from the arbitration unit 17 that has received the transmission request.

The buffer 162 temporarily holds transmission data (reception data) in order to transmit the data (transmission data) stored in the main memory 20 to the network 3 . Transmission data to be transmitted to the network 3 is stored in the buffer 162 by the DMAC 12 in a FIFO (first in, first out) manner.

The arbitration unit 17 coordinates multiple transmission requests to the network 3. In other words, when the transmission times TT of the transmission data stored in each of the plurality of buffers 162 are approximately the same, the arbitration unit 17 adjusts the transmission requests to the network 3. Decide whether to give priority to time transmission.
In other words, upon receiving transmission requests related to transmission data stored in each of the plurality of buffers 162 at substantially the same time, the arbitration unit 17 selects a transmission request to which access is granted.

Here, when the buffer 162 is roughly divided into a normal transmission buffer and a special transmission buffer, and receives transmission requests related to transmission data stored in each of the normal transmission buffer and the special transmission buffer, almost simultaneously, the arbitration unit 17 , perform the following processing. That is, the arbitration unit 17 gives priority to transmission requests related to transmission data stored in the special transmission buffer over transmission requests related to transmission data stored in the normal transmission buffer. In other words, the arbitration unit 17 grants access permission to a transmission request related to transmission data stored in the special transmission buffer.

§3. Operation example (Overview of processing executed by the communication controller)
FIG. 3 is a flow diagram illustrating an overview of processing executed by the communication controller 10.
As shown in FIG. 3, first, the descriptor execution management unit 13 (in particular, the selection unit 131) acquires at least one of the transmission time TT and priority P defined in each of the plurality of descriptors (S10). . Then, the selection unit 131 selects a descriptor to be read from among the plurality of descriptors based on the acquired "at least one of the transmission time TT and priority P of each of the plurality of descriptors" (S20). When selecting a descriptor to read, the selection unit 131 notifies the reading unit 132 of the selected descriptor.

The reading unit 132 reads the descriptor selected by the selection unit 131 (S30). The reading unit 132 sets the address (storage destination address in the main memory 20), the data size of the transmission data, etc. defined in the read descriptor in the DMAC 12 (S40).

The DMAC 12 transfers the transmission data stored in the main memory 20 to the buffer 162 (that is, stores the transmission data in the buffer 162) according to the contents set in S40 (S50). Then, the BUF management unit 16 transmits the transmission data stored in the buffer 162 (S60).

The processing executed by the communication controller 10, which has been explained using FIG. 3 so far, can be organized as follows. That is, the process (control method) executed by the communication controller 10 is to transfer data (transmission data) from the main memory 20 to the buffer 162 according to the read transmission descriptor, and to transmit the data transferred to the buffer 162. This is a control method.

The control method executed by the communication controller 10 includes a selection step (S20) and a reading step (S30). The selection step is a process of selecting a descriptor to be read from among the plurality of transmission descriptors based on at least one of "transmission time TT" and "priority P" defined in each of the plurality of transmission descriptors. . That is, the selection step is a process of selecting a transmission descriptor to be executed from among the plurality of transmission descriptors based on "at least one of transmission time TT and priority P" defined in each of the plurality of transmission descriptors. It is. Further, the reading step is a process of reading the transmission descriptor selected in the selection step, that is, a process of executing the transmission descriptor selected in the selection step.

According to the above configuration, the control method executed by the communication controller 10 selects one of the plurality of transmission descriptors from among the plurality of transmission descriptors based on at least one of the transmission time TT and the priority P defined in each of the plurality of transmission descriptors. , select the descriptor to read. The control method executed by the communication controller 10 is to read the selected transmission descriptor and transfer the transmission data from the main memory 20 to the buffer 162 in accordance with the read transmission descriptor. In other words, the control method executed by the communication controller 10 selects one descriptor to be read from among a plurality of transmission descriptors based on at least one of the transmission time TT and priority P of each of the plurality of transmission descriptors. do.

Therefore, the communication controller 10 that executes the control method does not need to include a plurality of transmission queues each including a DMAC and a transmission buffer, and the implementation size of the communication controller 10 can be reduced.

Further, the control method (that is, the control method executed by the communication controller 10) controls the output of processing results by software (processor) by controlling the reading order of a plurality of transmission descriptors. Control the order in which data is sent. That is, the software can treat the communication controller 10 that executes the control method as one piece of hardware that includes a plurality of transmission queues that manage "the transmission order and actual transmission time RTT of transmission data." Therefore, the control method can reduce the processing load of software related to output control of processing results (for example, management of "transmission order and actual transmission time RTT of transmission data").

Therefore, the control method executed by the communication controller 10 has the effect of reducing the processing load of software while suppressing the implementation size of the communication controller 10.

As described above, the communication controller 10 uses at least one of the transmission time TT and the priority P to select the descriptor to be read (that is, the descriptor to be executed), that is, the reading order (execution order) of the plurality of descriptors. control. Therefore, the communication controller 10 reduces the processing load on the software (that is, the CPU 30), particularly the processing load related to the management of the "transmission order and actual transmission time RTT of transmission data", while suppressing the implementation size. be able to.

Here, the developer of the communication controller 10 further assumes the following cases 1, 2, and 3, and appropriately determines the descriptor to be read even when the communication controller 10 faces these three cases. We designed it so that you can choose. Details will be explained below.

(In Case 1, when descriptors are selected only by priority)
FIG. 4 is a diagram illustrating a situation that occurs when, in case 1, a descriptor that should be executed first (that is, read first) is selected based only on the priority P in the descriptor. In case 1, the transmission time TT (low priority) specified by the descriptor to which a low priority P is set is earlier than the transmission time TT (high priority) specified by a descriptor to which a high priority P is set, and , the time interval between the two transmission times TT is large. Hereinafter, a descriptor to which a low priority P is set may be referred to as a "low priority descriptor", and a descriptor to which a high priority P is set may be referred to as a "high priority descriptor". In FIG. 4, the communication controller 10 is abbreviated as "NIC (Network Interface Card)."

In case 1 illustrated in FIG. 4, "9:05" is defined as the transmission time TT(0) of the transmission data D(0) in TX0, that is, the first descriptor memory 14(0), and A descriptor that defines "1" as the priority P of (0) is stored. Further, in TX1, that is, the second descriptor memory 14(1), "9:00" is defined as the transmission time TT(1) of the transmission data D(1), and the priority P of the transmission data D(1) is A descriptor that specifies "2" as "2" is stored.

That is, in case 1, a high priority descriptor is stored in TX0, and a low priority descriptor is stored in TX1. The "transmission time TT(0)" of the transmission data D(0) specified by the high priority descriptor stored in TX0 is "9:05", and the low priority descriptor stored in TX1 specifies The "transmission time TT(1)" of the transmission data D(1) is "9:00". The transmission time TT(1): "9:00" defined by the low priority descriptor is earlier than the transmission time TT(0): "9:05" defined by the high priority descriptor. Also, the time interval between the transmission time TT(1): "9:00" of the transmission data D(1) and the transmission time TT(0): "9:05" of the transmission data D(0) is " 5'', and the time interval between the two transmission times TT is large. In other words, the transmission time TT (low priority) specified by the low priority descriptor is earlier than the transmission time TT (high priority) specified by the high priority descriptor, and the transmission time TT (low priority) and the transmission time TT (high priority) are earlier than the transmission time TT (high priority) specified by the high priority descriptor. ) is large.

In case 1, if the descriptor to be executed first is selected based only on the "priority P" specified by the descriptor, the high priority descriptor stored in TX0 will be placed before the low priority descriptor stored in TX1. is executed.

Since the high-priority descriptor is executed before the low-priority descriptor, data D(0) corresponding to the high-priority descriptor is stored in the buffer 162 (BUF) before data D(1) corresponding to the low-priority descriptor. ).

In the example shown in FIG. 4, after data D(0) is stored in BUF0, that is, the first buffer 162(0), data D(1) is stored in BUF1, that is, the second buffer 162(1). has been done. Note that it is not essential to separate the buffer 162 that stores data D(0) and the buffer 162 that stores data D(1), and they may be stored in the same buffer 162. For example, data D(0) and data D(1) may be stored in the same buffer 162 in the order in which their corresponding descriptors were executed (read). In FIG. 4, to make it easier to understand that data D(0) is stored in the buffer 162 (BUF) before data D(1), data D(0) is stored in BUF0, and data This is merely an example of storing D(1) in BUF1.

Since data D(0) is stored in the buffer 162 before data D(1), transmission of data D(1) to network 3 is different from data D(0) being transmitted to network 3. executed later. That is, after the transmission data D(0) is transmitted to the network 3 at the transmission time TT(0): "9:05", the transmission of the data D(1) to the network 3 is executed. Therefore, the transmission data D(1) cannot be transmitted to the network 3 at "9:00", which is the transmission time TT(1).

(In Case 2, when a descriptor is selected only by transmission time)
FIG. 5 is a diagram illustrating a situation that occurs when, in case 2, a descriptor that should be executed first (that is, read first) is selected based only on the transmission time TT in the descriptor. In case 2, the transmission time TT (low priority) specified by the low priority descriptor is earlier than the transmission time TT (high priority) specified by the high priority descriptor, and the transmission time TT (low priority) and transmission time TT (high priority) are (priority) is small. In FIG. 5, the communication controller 10 is abbreviated as "NIC".

In case 2 illustrated in FIG. 5, in TX0, "9:01" is specified as the "transmission time TT(0)" of the transmission data D(0), and "priority P" of the transmission data D(0) is specified. A descriptor that specifies "1" as "1" is stored. Furthermore, in TX1, "9:00" is defined as the "transmission time TT(1)" of the transmission data D(1), and "2" is defined as the "priority P" of the transmission data D(1). Descriptors are stored.

That is, in case 2, a high priority descriptor is stored in TX0, and a low priority descriptor is stored in TX1. The "transmission time TT(0)" of the transmission data D(0) specified by the high priority descriptor stored in TX0 is "9:01", and the low priority descriptor stored in TX1 specifies The "transmission time TT(1)" of the transmission data D(1) is "9:00". The transmission time TT(0): "9:00" defined by the low priority descriptor is earlier than the transmission time TT(1): "9:01" defined by the high priority descriptor. Furthermore, the time interval between the transmission time TT(1): "9:00" of the transmission data D(1) and the transmission time TT(0): "9:01" of the transmission data D(0) is "1". ”, and the time interval between transmission time TT(1) and transmission time TT(0) is small. In other words, the transmission time TT (low priority) specified by the low priority descriptor is earlier than the transmission time TT (high priority) specified by the high priority descriptor, and the transmission time TT (low priority) and the transmission time TT (high priority) are earlier than the transmission time TT (high priority) specified by the high priority descriptor. ) is small.

In case 2, if a descriptor to be executed is selected based only on the "transmission time TT" specified by the descriptor, the low priority descriptor stored in TX1 will be executed before the high priority descriptor stored in TX0. be done.

Since the low priority descriptor is executed before the high priority descriptor, data D(1) corresponding to the low priority descriptor is transferred to the buffer 162 (BUF) before data D(0) corresponding to the high priority descriptor. ).

In the example shown in FIG. 5, after data D(1) is stored in BUF1, that is, the second buffer 162(1), data D(0) is stored in BUF0, that is, the first buffer 162(0). has been done. Note that it is not essential to separate the buffer 162 that stores data D(0) and the buffer 162 that stores data D(1), and they may be stored in the same buffer 162. For example, data D(0) and data D(1) may be stored in the same buffer 162 in the order in which their corresponding descriptors were executed (read). In FIG. 5, to make it easier to understand that data D(1) is stored in the buffer 162 (BUF) before data D(0), data D(0) is stored in BUF0, and data This is merely an example of storing D(1) in BUF1.

By storing data D(1) in the buffer 162 before data D(0), transmission of data D(0) to network 3 is different from data D(1) being transmitted to network 3. executed later. That is, after the transmission data D(1) is transmitted to the network 3 at its transmission time TT(1): "9:00", the transmission of the data D(0) to the network 3 is executed. Therefore, the transmission data D(0) cannot be transmitted to the network 3 at "9:01", which is the transmission time TT(0).

(Devices assuming Case 1 and Case 2)
The developer of the communication controller 10 has further devised the communication controller 10 so that the communication controller 10 can suitably select the descriptor to be read in both case 1 and case 2 described above.

Specifically, the communication controller 10 executes the following process when "the transmission time TT (low priority) specified by the low priority descriptor is earlier than the transmission time TT (high priority) specified by the high priority descriptor". . That is, the communication controller 10 adds the transfer time RT of the data corresponding to the high priority descriptor (high priority data) and the transfer time RT of the data corresponding to the low priority descriptor (low priority data) to the current time CT. Calculate the time (scheduled total time ERT). In other words, the communication controller 10 calculates "scheduled total time ERT = current time CT + high priority data transfer time RT + low priority data transfer time RT". “Transfer time RT” is the time (period) required to transfer certain data (certain transmission data) from main memory 20 to buffer 162.

Next, the communication controller 10 compares the calculated scheduled total time ERT with the transmission time TT (high priority) of the high priority data.

Here, if the scheduled total time ERT is larger (later) than the transmission time TT (high priority), the communication controller 10 transfers the high priority data to the buffer 162 even after transferring the low priority data to the buffer 162. Transfer can be made in time for transmission time TT (high priority). In other words, if the scheduled total time ERT is later than the transmission time TT (high priority), the communication controller 10 transfers the high priority data before the transmission time TT (high priority) even after transferring the low priority data to the buffer 162. Data may be transferred to buffer 162.

Therefore, if the scheduled total time ERT is later than the transmission time TT (high priority), the communication controller 10 selects a low priority descriptor, executes (reads) the low priority descriptor, and then executes (reads) the high priority descriptor. ).

Further, if the scheduled total time ERT is smaller (earlier) than the transmission time TT (high priority), the communication controller 10 transmits the high priority data to the buffer 162 after transmitting the low priority data to the buffer 162. It is not possible to make it in time for time TT (high priority). In other words, if the scheduled total time ERT is earlier than the transmission time TT (high priority), the communication controller 10 transfers the high priority data to the buffer before the transmission time TT (high priority) after transmitting the low priority data to the buffer 162. 162 cannot be transferred.

Therefore, if the scheduled total time ERT is earlier than the transmission time TT (high priority), the communication controller 10 selects the high priority descriptor, executes (reads) the high priority descriptor, and then executes (reads) the low priority descriptor. ).

FIG. 6 is a flow diagram illustrating an example of a selection process (process of selecting a descriptor to be read, that is, a descriptor to be executed) executed by the selection unit 131 in consideration of both the priority P and the transmission time TT. It is. Specifically, FIG. 6 shows the process of "selecting which descriptor should be executed first (read first) among the high-priority descriptor and the low-priority descriptor" executed by the selection unit 131. It is a flow diagram explaining details.

As shown in FIG. 6, the selection unit 131 first determines whether the transmission time TT of the low priority descriptor (low priority) is earlier than the transmission time TT of the high priority descriptor (high priority) (S110 ). If “the transmission time TT (high priority) is earlier than the transmission time TT (low priority), or they are the same” (NO in S110), the selection unit 131 selects the high priority descriptor and the low priority descriptor. Among them, a high priority descriptor is selected (S140).

If "the transmission time TT (low priority) is earlier than the transmission time TT (high priority)" (YES in S110), the selection unit 131 calculates the scheduled total time ERT (S120). As mentioned above, the scheduled total time ERT is calculated by adding the data transfer time RT (low priority) corresponding to the low priority descriptor and the data transfer time RT (high priority) corresponding to the high priority descriptor to the current time CT. It is the time when

Then, the selection unit 131 determines whether "the scheduled total time ERT is greater than the transmission time TT (high priority) defined in the high priority descriptor (the scheduled total time ERT is later)" (S130). If “the scheduled total time ERT is later than the transmission time TT (high priority)” (YES in S130), the selection unit 131 selects the high priority descriptor from the high priority descriptor and the low priority descriptor (S140) .

If "the scheduled total time ERT is earlier than the transmission time TT (high priority), or the two are the same" (NO in S130), the selection unit 131 selects the low priority descriptor between the high priority descriptor and the low priority descriptor. is selected (S140).

(Results of selection of communication controller according to this embodiment for case 1 and case 2)
FIG. 7 is a diagram illustrating descriptors selected by the selection unit 131 when the selection unit 131 executes the flow illustrated in FIG.

As mentioned above, in case 1, in TX0, "9:05" is defined as the "transmission time TT(0)" of the transmission data D(0), and "9:05" is defined as the "priority P" of the transmission data D(0). A high priority descriptor specifying "1" is stored. Furthermore, in TX1, "9:00" is defined as the "transmission time TT(1)" of the transmission data D(1), and "2" is defined as the "priority P" of the transmission data D(1). Contains low priority descriptors.

Here, the transfer time RT (high priority) required to transfer the data corresponding to the high priority descriptor (high priority data) from the main memory 20 to the buffer 162 is "2". Further, the transfer time RT (low priority) required to transfer data corresponding to a low priority descriptor (low priority data) from the main memory 20 to the buffer 162 is "2". The current time CT is "08:58". Therefore, when a high-priority descriptor is executed after a low-priority descriptor is executed, the time when the transfer of high-priority data from the main memory 20 to the buffer 162 is completed (that is, the scheduled total time ERT) is 09:02. ”.

Here, the scheduled total time ERT "09:02" is earlier than the transmission time TT (high priority): "9:05". Therefore, the selection unit 131 selects the low priority descriptor (the descriptor stored in TX1) from the high priority descriptor and the low priority descriptor, and the communication controller 10 first executes (reads) the low priority descriptor. .

As mentioned above, in case 2, in TX0, "9:01" is specified as the "transmission time TT(0)" of the transmission data D(0), and "9:01" is defined as the "priority P" of the transmission data D(0). A high priority descriptor specifying "1" is stored. Furthermore, in TX1, "9:00" is defined as the "transmission time TT(1)" of the transmission data D(1), and "2" is defined as the "priority P" of the transmission data D(1). Contains low priority descriptors.

Here, the transfer time RT (high priority) required to transfer the data corresponding to the high priority descriptor (high priority data) from the main memory 20 to the buffer 162 is "2". Further, the transfer time RT (low priority) required to transfer data corresponding to a low priority descriptor (low priority data) from the main memory 20 to the buffer 162 is "2". The current time CT is "08:58". Therefore, when a high-priority descriptor is executed after a low-priority descriptor is executed, the time when the transfer of high-priority data from the main memory 20 to the buffer 162 is completed (that is, the scheduled total time ERT) is 09:02. ”.

Here, the scheduled total time ERT "09:02" is later than the transmission time TT (high priority): "9:01". Therefore, the selection unit 131 selects the high priority descriptor (the descriptor stored in TX0) from the high priority descriptor and the low priority descriptor, and the communication controller 10 first executes (reads) the high priority descriptor. .

(For case 1, when descriptors are selected taking into consideration priority and transmission time)
FIG. 8 is a diagram showing a specific example of processing when the flow illustrated in FIG. 6 is executed for case 1. As mentioned above, when the high priority descriptor is executed after the low priority descriptor is executed, the time when the transfer of the high priority data from the main memory 20 to the buffer 162 is completed (that is, the scheduled total time ERT) is "09". :02''. The scheduled total time ERT "09:02" is earlier than the transmission time TT (high priority): "9:05" defined in the high priority descriptor in case 1.

Therefore, the selection unit 131 selects the low priority descriptor (the descriptor stored in TX1) from the high priority descriptor and the low priority descriptor, and the communication controller 10 first executes (reads) the low priority descriptor. .

Since the low priority descriptor is executed before the high priority descriptor, data D(1) corresponding to the low priority descriptor is transferred to the buffer 162 (BUF) before data D(0) corresponding to the high priority descriptor. ).

Therefore, after the data D(1) stored in the buffer 162 first is transmitted, the data D(0) stored in the buffer 162 after the data D(1) is transmitted. Specifically, the communication controller 10 (in particular, the time specified transmission management unit 161) transfers the data D(1) previously stored in the buffer 162 to the "transmission time TT(1)" of the transmission data D(1). It is transmitted at "9:00". Then, after transmitting the data D(1), the communication controller 10 (in particular, the time specified transmission management unit 161) transfers the data D(0) stored in the buffer 162 after the data D(1) to the transmission data D It is transmitted at "9:05" which is "transmission time TT(0)" of (0).

Therefore, in case 1, the communication controller 10 transmits the low priority data according to the transmission time TT (low priority) of the low priority descriptor, and transmits the high priority data according to the transmission time TT (high priority) of the high priority descriptor. Data can be sent.

(For case 2, when descriptors are selected taking into consideration priority and transmission time)
FIG. 9 is a diagram showing a specific example of processing when the flow illustrated in FIG. 6 is executed for case 2. As mentioned above, when the high priority descriptor is executed after the low priority descriptor is executed, the time when the transfer of the high priority data from the main memory 20 to the buffer 162 is completed (that is, the scheduled total time ERT) is "09". :02''. The scheduled total time ERT "09:02" is later than the transmission time TT (high priority): "9:01" defined in the high priority descriptor in case 2.

Therefore, the selection unit 131 selects the high priority descriptor (the descriptor stored in TX0) from the high priority descriptor and the low priority descriptor, and the communication controller 10 first executes (reads) the high priority descriptor. .

Since the high-priority descriptor is executed before the low-priority descriptor, data D(0) corresponding to the high-priority descriptor is stored in the buffer 162 (BUF) before data D(1) corresponding to the low-priority descriptor. ).

Therefore, after the data D(0) stored in the buffer 162 first is transmitted, the data D(1) stored in the buffer 162 after the data D(0) is transmitted. Specifically, the communication controller 10 (in particular, the time specified transmission management unit 161) transfers the data D(0) previously stored in the buffer 162 to the "transmission time TT(0)" of the transmission data D(0). It is transmitted at "9:01". Then, after transmitting the data D(0), the communication controller 10 (in particular, the time specified transmission management unit 161) transmits the data D(1) stored in the buffer 162 after the data D(0) at the earliest possible timing. And send it.

Therefore, in case 2, the communication controller 10 can transmit the high priority data according to the transmission time TT (high priority) of the high priority descriptor, and can also transmit the low priority data at the earliest possible time.

The contents that have been explained using FIGS. 4 to 9 can be summarized as follows. That is, regarding the communication controller 10, when the priority P of a certain transmission descriptor among the plurality of transmission descriptors is higher than the priority P of another descriptor, the selection unit 131 executes the following process. First, the selection unit 131 selects a scheduled total time that is "the time obtained by adding the current time CT, the transfer time RT of data corresponding to that certain transmission descriptor, and the transfer time RT of data corresponding to that other descriptor." Calculate ERT. The transfer time RT is the time required to transfer data (transmission data) from the main memory 20 to the buffer 162. Then, the selection unit 131 compares the calculated scheduled total time ERT with the transmission time TT of that certain transmission descriptor.

If the transmission time TT of the certain transmission descriptor is later (later) than the scheduled total time ERT, the selection unit 131 selects another descriptor in preference to the certain transmission descriptor. Furthermore, if the transmission time TT of that certain transmission descriptor is before the scheduled total time ERT, the selection unit 131 selects that certain transmission descriptor in preference to another descriptor.

According to the above configuration, when the priority P of a certain transmission descriptor is higher than the priority P of another descriptor, the communication controller 10 sets the scheduled total time ERT and the transmission time TT of that certain transmission descriptor. Compare. If the transmission time TT of that certain transmission descriptor is later (later) than the scheduled total time ERT, the communication controller 10 selects another descriptor in preference to that certain transmission descriptor. Further, if the transmission time TT of that certain transmission descriptor is before the scheduled total time ERT, the communication controller 10 selects that certain transmission descriptor in preference to another descriptor.

Here, if a descriptor to be read is selected based only on the priority P specified for each of the plurality of transmission descriptors, the descriptor with a lower priority P is always read after the descriptor with a higher priority P. (to be carried out).

However, if the transmission time TT of another descriptor whose priority P is lower than that of a certain transmission descriptor is sufficiently earlier than the transmission time TT of that certain transmission descriptor, the reading order of descriptors may be determined only according to the priority P. is not necessarily appropriate.

For example, even after transmitting data corresponding to another descriptor is transferred to the main memory, transmitting data corresponding to a certain transmitting descriptor is transferred to the main memory before the transmitting time TT of that transmitting descriptor. In some cases, the data can be transferred to the memory 20. In such a case, the certain descriptor may be read after the other descriptor is read (executed), that is, the other descriptor should be read before the certain send descriptor.

Furthermore, if a descriptor to be read is selected based only on the transmission time TT specified for each of a plurality of descriptors, a descriptor with a later transmission time TT will always be read after a descriptor with an earlier transmission time TT. become.

However, if the transmission time TT of another descriptor whose priority P is lower than that of a certain descriptor is immediately before the transmission time TT of that certain descriptor, determining the reading order of descriptors only according to the transmission time TT is not possible. Not necessarily appropriate.

For example, after the transmission data corresponding to another descriptor is transferred to the main memory 20, the transmission data corresponding to that certain transmission descriptor is transferred to the main memory 20 before the transmission time TT of that certain transmission descriptor. It may not be possible to transfer to. In such a case, that one descriptor must be read before that other descriptor is read (executed), that is, that one descriptor should be read before that other send descriptor. be.

The communication controller 10 compensates for the above-mentioned deficiencies of determining the descriptor reading order only according to the priority P and determining the descriptor reading order only according to the transmission time TT. That is, when the priority P of a certain transmission descriptor among the plurality of transmission descriptors is higher than the priority P of another descriptor, the communication controller 10 sets the scheduled total time ERT and the transmission time TT of a certain transmission descriptor. Compare. Then, the communication controller 10 selects a descriptor to be read, that is, a descriptor to be executed, based on the comparison result between the scheduled total time ERT and the transmission time TT of a certain transmission descriptor.

Therefore, the communication controller 10 has the effect of being able to appropriately select a descriptor to be read, compared to a method of selecting a descriptor to be read based only on either the priority P or the transmission time TT.

(Example of calculation of transfer time)
FIG. 10 is a table in which the communication controller 10 organizes information used when calculating the transfer time RT for certain transmission data. Specifically, the communication controller 10 (in particular, the selection unit 131) selects the data size of certain transmission data and "the transfer speed at which the communication controller 10 transfers data from the main memory 20 to the buffer 162." From this, the transfer time RT of certain transmission data is calculated.

The communication controller 10 acquires the theoretical speed (transfer rate) related to data transfer between the main memory 20 and the communication controller 10 (especially the buffer 162) when the PLC 1 is activated (especially when establishing the protocol). I can do it. For example, when the main memory 20 and the communication controller 10 are connected by PCIe (Peripheral Component Interconnect Express), the communication controller 10 checks the rate (theoretical value) guaranteed by the PCIe standard by referring to a register. .

Here, each of the "execution rate" and "overhead" is prepared in advance for each rate (theoretical value). Specifically, the "execution rate" is tuned for each rate (theoretical value) during production (development) of the communication controller 10. The "execution rate" may be set by software (that is, the CPU 30) when the PLC 1 is started. Similarly, "overhead" is tuned for each rate (theoretical value) during production (development) of the communication controller 10.

The communication controller 10 obtains the "execution rate" corresponding to the confirmed rate (theoretical value), and calculates the "transfer rate" from the rate (theoretical value) and the execution rate. Further, the communication controller 10 uses "overhead" prepared in advance for each rate (theoretical value) to calculate the transfer time RT of certain data.

Since the data size (transfer size) of the transmission data is written in the transmission descriptor, the communication controller 10 can acquire the transfer size of the transmission data every time the transmission descriptor is read.

The communication controller 10 (in particular, the selection unit 131) uses the following formula to select the transmission data based on the transmission size of the acquired transmission data and the "transfer speed" and "overhead" for each rate (theoretical value). Calculate the transfer time RT. That is, the communication controller 10 calculates the transfer time RT of the transmission data from "transfer time RT = {overhead + (transfer size/transfer rate)}".

(About case 3)
FIG. 11 is a diagram illustrating a situation that occurs when the determination time JT (details will be described later) is not provided in case 3. In case 3, a certain descriptor defines a time that is a predetermined time or more away from the current time CT as a "transmission time TT." In FIG. 11, the communication controller 10 is abbreviated as "NIC".

In case 3 illustrated in FIG. 11, in TX0, "9:10" is defined as the "transmission time TT(0)" of the transmission data D(0), and "priority P" of the transmission data D(0) is specified. A descriptor that specifies "1" as "1" is stored. Furthermore, in TX1, "9:00" is defined as the "transmission time TT(1)" of the transmission data D(1), and "1" is defined as the "priority P" of the transmission data D(1). Descriptors are stored. Further, in TX2, that is, the third descriptor memory 14(2), "9:00" is defined as the "transmission time TT(2)" of the transmission data D(2), and "9:00" is defined as the "transmission time TT(2)" of the transmission data D(2). A descriptor that defines "2" as "Priority P" is stored.

Here, after executing (reading) the "high priority descriptor stored in TX0", each of the "high priority descriptor stored in TX1" and "low priority descriptor stored in TX2" is executed. Then, the situation shown in FIG. 11 occurs. Note that even if the "high priority descriptor stored in TX1" is executed after the "high priority descriptor stored in TX0" is executed, the "low priority descriptor stored in TX2" is executed first. It's okay if it's ahead.

That is, when the "high priority descriptor stored in TX0" is executed first, the high priority data D(0) corresponding to the "high priority descriptor stored in TX0" is stored at the beginning of the buffer 162. Ru.

The "high priority descriptor stored in TX1" is executed after the "high priority descriptor stored in TX0". Therefore, the high priority data D(1) corresponding to the "high priority descriptor stored in TX1" is stored in the buffer 162 after the high priority data D(0).

Since high-priority data D(0) is stored in the buffer 162 before high-priority data D(1), it is necessary to send high-priority data D(0) to the network 3 before transmitting high-priority data. Data D(1) cannot be sent to network 3.

Here, as mentioned above, the "transmission time TT(1)" of the transmission data D(1) is "9:00", whereas the "transmission time TT(0)" of the transmission data D(0) is "9:00". is "9:10". Therefore, transmission data D(1) cannot be transmitted to network 3 at "9:00", and transmission data D(0) cannot be transmitted to network 3 at "9:00". 10” after sending it to network 3.

As shown in FIG. 11, in case 3, a descriptor (for example, "transmission time TT" in FIG. "High priority descriptor stored in TX0") has occurred. In case 3, after the descriptor that defines the transmission time TT(0) as the "transmission time TT", "transmission time TT (for example, transmission time TT(1)) which is closer to the current time CT than the transmission time TT(0)" is added. ) is generated as the "transmission time TT."

In case 3, the "descriptor that specifies transmission time TT (0) as 'transmission time TT'" that occurred earlier is placed before the 'descriptor that specifies transmission time TT (1) as 'transmission time TT'''. If this is executed, the situation shown in FIG. 11 will occur. In other words, the data corresponding to the "descriptor that defines the transmission time TT(0) as the 'transmission time TT'" becomes an obstacle, and the data corresponding to the "descriptor that defines the transmission time TT(1) as the 'transmission time TT'" gets in the way. cannot be transmitted at transmission time TT(1).

(Devices assuming Case 3)
The developer of the communication controller 10 has further devised the following ideas for the communication controller 10 so that the communication controller 10 can suitably select the descriptor to be read even in the case 3 described above.

That is, the communication controller 10 is provided with a determination time JT in advance, and the communication controller 10 uses the determination time JT to adjust the timing of executing (reading) a descriptor. Specifically, the communication controller 10 reads (executes) the descriptor after "the time that is the determination time JT back from the transmission time TT specified by the descriptor."

The communication controller 10 determines that if the period obtained by subtracting the "current time CT" from the "transmission time TT specified in the descriptor" is greater than the determination time JT, that is, "(transmission time TT - current time CT) > determination time JT". ”, then do not execute that descriptor. The communication controller 10 determines that when the period obtained by subtracting the "current time CT" from the "transmission time TT specified by the descriptor" is less than or equal to the determination time JT, that is, "(transmission time TT - current time CT) ≦ determination time JT". Then, execute that descriptor.

FIG. 12 is a diagram showing a specific example of processing implemented by the communication controller 10 provided with the determination time JT for case 3. As mentioned above, in case 3, "9:10" is specified as the "transmission time TT (0)" of the transmission data D (0) in TX0, and "priority P" of the transmission data D (0) is specified. A descriptor specifying "1" is stored. Furthermore, in TX1, "9:00" is defined as the "transmission time TT(1)" of the transmission data D(1), and "1" is defined as the "priority P" of the transmission data D(1). Descriptors are stored. Furthermore, in TX2, "9:00" is defined as the "transmission time TT(2)" of the transmission data D(2), and "2" is defined as the "priority P" of the transmission data D(2). Descriptors are stored.

The communication controller 10 uses the descriptor that specifies "9:10" as the "transmission time TT(0)" of the transmission data D(0) until "the time from '9:10' back to the determination time JT". , not executed. That is, the communication controller 10 does not read (does not execute) the descriptor that defines the transmission time TT while "the time (period) obtained by subtracting the current time CT from the transmission time TT is greater than the determination time JT."

Then, the communication controller 10 replaces the descriptor that specifies "9:00" as the "transmission time TT(1)" of the transmission data D(1) with "the period obtained by subtracting the current time CT from '9:00'". When the judgment time JT or less is reached, the process is executed. In other words, when "the time obtained by subtracting the current time CT from the transmission time TT is less than or equal to the determination time JT", the communication controller 10 regards the descriptor that defines the transmission time TT as the descriptor to be read. In other words, the selection unit 131 be subject to selection processing.

Therefore, the communication controller 10 executes the "high priority descriptor stored in TX1" before the "high priority descriptor stored in TX0". Therefore, the communication controller 10 stores the high priority data D(1) corresponding to the "high priority descriptor stored in TX1" in the buffer 162 before the high priority data D(0).

Since the high priority data D(1) is stored in the buffer 162 before the high priority data D(0), the communication controller 10, before transmitting the high priority data D(0) to the network 3, Transmission high priority data D(1) can be transmitted to the network 3. Specifically, after transmitting the high-priority transmission data D(1) to the network 3 at transmission time TT(1): "9:00", the communication controller 10 transmits the high-priority transmission data D(0) to the network 3. Transmission time TT(0): Transmitted to network 3 at "9:10".

The content that has been explained using FIGS. 11 and 12 can be summarized as follows. That is, in the communication controller 10, the determination time JT is set in advance, and the reading unit 132 reads the transmission descriptor after the determination time JT goes back from the transmission time TT of the transmission descriptor.

According to the above configuration, the communication controller 10 reads the transmission descriptor after the determination time JT has passed back from the transmission time TT of the transmission descriptor.

Here, after reading a certain transmission descriptor, if another descriptor is generated whose transmission time TT is closer to the current time CT than the transmission time TT of that certain transmission descriptor, the following problem will occur. . That is, a problem arises in that the data corresponding to that certain transmission descriptor becomes a failure and the data corresponding to that other descriptor cannot be transmitted at the transmission time TT of that other descriptor.

This is because the data stored in the buffer 162 is transmitted in the order in which it was stored. In other words, if data corresponding to one transmission descriptor is stored before data corresponding to another descriptor, data corresponding to that other descriptor must be stored after the data corresponding to that one transmission descriptor is transmitted. No data is sent. Then, the data corresponding to that certain transmission descriptor is not transmitted until the transmission time TT of that certain transmission descriptor arrives. However, since the transmission time TT of that certain transmission descriptor is later than the transmission time TT of that other descriptor, the data corresponding to that other descriptor cannot be transmitted at the transmission time TT of that other descriptor. I can't.

Therefore, the communication controller 10 suppresses the possibility that the above-mentioned problem will occur by reading the transmission descriptor after the determination time JT has elapsed from the transmission time TT of the transmission descriptor. That is, the communication controller 10 performs the above-mentioned procedure so as not to read a certain transmission descriptor before reading another descriptor whose transmission time TT is closer to the current time CT than the transmission time TT of the transmission descriptor. Perform adjustments. In other words, the communication controller 10 adjusts the reading time (execution time) of a certain transmission descriptor, and specifically, the communication controller 10 adjusts the reading time (execution time) of the certain transmission descriptor, and specifically, the communication controller 10 adjusts the reading time (execution time) of the certain transmission descriptor, and specifically, after the judgment time JT goes back from the transmission time TT of the certain transmission descriptor. , reads (executes) that certain send descriptor.

Therefore, the communication controller 10 can prevent a certain transmission descriptor from being read before reading another descriptor whose transmission time TT is closer to the current time CT than the transmission time TT of the certain transmission descriptor. It has the effect of

(Regarding the processing executed by the communication controller corresponding to cases 1, 2, and 3)
So far, it has been explained that in each of Case 1, Case 2, and Case 3, the communication controller 10 can execute (read) a plurality of descriptors to be executed in a desired order and at a desired timing. The processing executed by the communication controller 10 will be described below with reference to FIGS. 13 to 17.

(Example of processing executed by CPU and requester)
FIG. 13 is a flowchart showing an example of processing executed by the CPU 30 and the requester 15. Particularly, (A) in FIG. 13 shows an example of processing executed by the CPU 30, and (B) in FIG. An example of the processing to be executed is shown.

As shown in FIG. 13A, when there is a transmission request, the CPU 30 sets the transmission data in the main memory 20 (S210), that is, stores the transmission data in the main memory 20. Further, the CPU 30 sets the transmission descriptor in the main memory 20 (S220), that is, stores the transmission descriptor in the main memory 20. Then, the CPU 30 outputs a transmission request to the communication controller 10 (S230), and specifically notifies the communication controller 10 of the execution number and number of executions of the transmission descriptor.

“Number of executions” is the number of transmission data that the CPU 30 requests the communication controller 10 to execute; in other words, it is the number of transmission descriptors to be executed by the communication controller 10. Further, "execution number" indicates the number of the requester 15 and also indicates the number of the descriptor memory 14. For example, if the number of executions is "n", the communication controller 10 is notified of execution numbers from "0" to "n-1". The execution number and the number of executions are stored (set) in the setting register 151 of the requester 15, for example.

Since the communication controller 10 executes the transmission process, the process that should be executed by the CPU 30 ends at S230. If there is a separate transmission request, the CPU 30 may execute the processes from S210 to S230 each time.

As shown in FIG. 13B, first, the requester 15 determines whether there is a transmission request from the CPU 30 (S310). If there is no transmission request from the CPU 30 (NO in S310), the requester 15 waits until there is a transmission request from the CPU 30.

When there is a transmission request from the CPU 30 (YES in S310), the communication controller 10 (in particular, the requester 15) executes the following process. That is, the communication controller 10 that has received the transmission request from the CPU 30 acquires the descriptor stored in the main memory 20 in accordance with the received transmission request, and stores the acquired descriptor in the descriptor memory 14. Specifically, the descriptor to be obtained from the main memory 20 is specified based on the "number of executions" set in the setting register 151 of the requester 15 by the CPU 30, and the specified descriptor is obtained from the main memory 20. Then, the communication controller 10 (in particular, the requester 15) stores the obtained descriptor in "the descriptor memory 14 (area of the descriptor memory 14) corresponding to the 'execution number' set in the setting register 151 of the requester 15". do. For example, when the number of executions is "n", the "n" descriptors acquired from the main memory 20 are stored in the descriptor memory 14 from the first descriptor memory 14(0) to the n-th descriptor memory 14(n- 1).

Further, the communication controller 10 that has received the transmission request from the CPU 30 stores "1" in the request register of the requester 15 corresponding to the descriptor memory 14 that stores the descriptor according to the received transmission request. For example, when the communication controller 10 stores the descriptor A acquired in accordance with the transmission request in the first descriptor memory 14(0), the communication controller 10 stores the request register of the first requester 15(0) corresponding to the first descriptor memory 14(0) as " 1" is stored. Furthermore, when the communication controller 10 stores the descriptor B acquired in accordance with the transmission request in the second descriptor memory 14(1), the communication controller 10 writes " 1" is stored.

The requester 15 in which "1" is stored in the request register outputs "request signal = 1" to the descriptor execution management unit 13 to notify that "there is a transmission descriptor to be executed (read)" (S320). . Then, the requester 15 determines whether there is a transfer completion notification from the descriptor execution management unit 13 (S330).

If there is no transfer completion notification from the descriptor execution management unit 13 (NO in S330), the requester 15 waits until there is a transfer completion notification from the descriptor execution management unit 13.

When receiving the transfer completion notification from the descriptor execution management unit 13 (YES in S330), the requester 15 stores “0” in the request register and also outputs “request signal = 0” to the descriptor execution management unit 13. (S340). “Request signal=0” is a signal that notifies the descriptor execution management unit 13 that “there is no descriptor to be executed.”

(Example of processing executed by the descriptor execution management unit, BUF management unit, etc.)
FIG. 14 is a flowchart showing an example of processing executed by the descriptor execution management unit 13, BUF management unit 16, etc. In particular, (A) in FIG. 14 shows an example of processing executed by the descriptor execution management unit 13. , FIG. 14(B) shows an example of processing executed by the requester 15.

As shown in FIG. 14A, the descriptor execution management unit 13 determines whether there is a request from the requester 15 (“request signal = 1”; specifically, a transmission descriptor execution request (read request)). A determination is made (S410). If there is no request from the requester 15 (NO in S410), the descriptor execution management unit 13 waits until there is a request from the requester 15.

When there is a request from the requester 15 (YES in S410), the descriptor execution management unit 13 executes a selection process to select a transmission descriptor to be executed (that is, a transmission descriptor to be read) (S420). Details of the selection process will be described later with reference to FIGS. 15 to 17.

The descriptor execution management unit 13 executes the transmission descriptor selected in the selection process of S420, that is, reads the selected transmission descriptor. Then, the descriptor execution management unit 13 outputs a transfer request to the DMAC 12 according to the content specified in the read transmission descriptor (S430). The transfer request is a transfer instruction to the DMAC 12, and specifically, "Acquires transmit data from the main memory 20 according to the contents specified in the read transmit descriptor, and transfers the acquired transmit data to the buffer 162." Instructs the DMAC 12 to do the following.

The descriptor execution management unit 13 determines whether there is a transfer completion report from the DMAC 12 indicating that "the DMAC 12 has completed the transfer process of the transmission data corresponding to the transfer request" (S440). If there is no transfer completion report from the DMAC 12 (NO in S440), the descriptor execution management unit 13 waits until there is a transfer completion report from the DMAC 12.

When receiving the transfer completion report from the DMAC 12 (S440: YES), the descriptor execution management unit 13 issues a transfer completion notification to the requester 15 (S450). The "transfer completion notification" is information indicating that "transfer processing of transmission data from the main memory 20 to the buffer 162 has been completed in accordance with the contents specified in the transmission descriptor."

As shown in FIG. 14B, first, the BUF management unit 16 determines whether there is transmission data in the buffer 162 (S510). If there is no transmission data in the buffer 162 (NO in S510), the BUF management unit 16 waits until transmission data exists in the buffer 162.

If there is transmission data in the buffer 162 (S510: YES), the time-specific transmission management unit 161 determines whether "the current time CT is the transmission time TT of the transmission data existing in the buffer 162" (S520). If the current time CT is not the transmission time TT of the transmission data existing in the buffer 162 (NO in S520), the time specified transmission management unit 161 waits until the current time CT reaches the transmission time TT of the transmission data existing in the buffer 162. I'll keep it.

When the current time CT reaches the transmission time TT of the transmission data existing in the buffer 162 (S520: YES), the time-specified transmission management section 161 issues a transmission request to the arbitration section 17 (S530). The "transmission request" is information that "instructs the arbitration unit 17 to transmit the transmission data existing in the buffer 162."

The arbitration unit 17 checks whether “transmission of other transmission data is in progress” and, when confirming that transmission of other transmission data is not in progress, outputs access permission to the time-specified transmission management unit 161. do. The arbitration unit 17 does not output access permission to the time-specified transmission management unit 161 while transmitting other transmission data.

The time-specific transmission management unit 161 determines whether there is access permission from the arbitration unit 17 (S540). If there is no access permission from the arbitration unit 17 (NO in S540), the time specified transmission management unit 161 (BUF management unit 16) waits until access permission is obtained from the arbitration unit 17.

If there is access permission from the arbitration unit 17 (YES in S540), the time-specific transmission management unit 161 (BUF management unit 16) executes transmission of the transmission data existing in the buffer 162 (S550).

(Detailed example of selection process)
FIG. 15 is a flow diagram illustrating an example of the selection process (S420) illustrated in FIG. 14(A). As mentioned above, the descriptor execution management unit 13 determines the execution order of one or more transmission descriptors to be executed (read), and selects the transmission descriptor to be executed from among the plurality of transmission descriptors to be executed, for example. Select them one by one (selection process). The selection process executed by the descriptor execution management unit 13 will be described in detail below with reference to FIGS. 15 to 17.

As shown in FIG. 15, the descriptor execution management unit 13 sets, for example, "0" in each of three variables: current transmission time CST, current priority CPR, and current transfer time CRT (S1100). Hereinafter, the current transmission time CST, current priority CPR, and current transfer time CRT may be collectively referred to as a "current variable."

Next, the descriptor execution management unit 13 selects one arbitrary descriptor (=target descriptor) from among the one or more descriptors, each of which corresponds to the transmission request, and selects the priority P of the target descriptor, the transmission Time TT etc. are acquired (S1200). "One or more descriptors each corresponding to a transmission request" is "a descriptor for which a transmission request has been made (YES in S310) in (B) of FIG. 13".

In the following explanation, the "transmission time TT" specified by the target descriptor is abbreviated as "NST", and the "priority P" specified by the target descriptor is abbreviated as "NPR", which corresponds to the target descriptor. "Transfer time RT" of transmission data is abbreviated as "NRT". Further, transmission data corresponding to a target descriptor may be abbreviated as "target data." Similarly, the descriptor that defines the contents corresponding to the current transmission time CST, current priority CPR, and current transfer time CRT is abbreviated as "current descriptor", and the transmission data corresponding to the current descriptor is abbreviated as "current". There are things to do.

Then, the descriptor execution management unit 13 determines whether "the time (period) obtained by subtracting the current time CT from the transmission time NST of the target descriptor" is less than or equal to the determination time JT (S1300). If the time obtained by subtracting the current time CT from the transmission time NST of the target descriptor is greater than the determination time JT (NO in S1300), the descriptor execution management unit 13 checks whether "all descriptors for which transmission requests have been requested have been determined." (S1600). If the time obtained by subtracting the current time CT from the transmission time NST of the target descriptor is less than or equal to the determination time JT (YES in S1300), the descriptor execution management unit 13 compares the current priority CPR and the priority NPR of the target descriptor. (S1400).

Here, the process of S1300 is explained using FIG. 12, "The communication controller 10 reads the descriptor (execution ).

That is, in S1300, if the current time CT is smaller than "the time obtained by subtracting the determination time JT from the transmission time TT specified by a certain descriptor", the descriptor execution management unit 13 determines that the certain descriptor is not transmitted at the current time CT. Exclude from selection processing. If the current time CT is earlier than "the time that is the determination time JT from the transmission time TT specified by a certain descriptor", the descriptor execution management unit 13 executes the selection process for that certain descriptor at the current time CT. and does not read that certain descriptor.

In S1300, if the current time CT is equal to or greater than "the time obtained by subtracting the determination time JT from the transmission time TT specified by a certain descriptor", the descriptor execution management unit 13 selects that certain descriptor at the current time CT. Subject to processing. If the current time CT is after "the time that is the determination time JT from the transmission time TT specified by a certain descriptor" or later, the descriptor execution management unit 13 performs selection processing for that certain descriptor at the current time CT. Execute.

The descriptor execution management unit 13, which has compared the current priority CPR and the priority NPR of the target descriptor in S1400, executes an update process for each relationship between the current priority CPR and the priority NPR of the target descriptor (S1500). Specifically, the descriptor execution management unit 13 determines whether the priority NPR of the target descriptor is (1) the same as the current priority CPR, (2) higher than the current priority CPR, or (3) higher than the current priority CPR. For each lower case, perform an update process. Details of the update process executed by the descriptor execution management unit 13 for each relationship between the current priority CPR and the priority NPR of the target descriptor will be described with reference to FIGS. 16 and 17.

After executing the update process in S1500, the descriptor execution management unit 13 confirms whether "all descriptors for which transmission requests have been requested have been determined" (S1600). For example, the descriptor execution management unit 13 checks whether "the processes from S1200 (or S1700) to S1500 have been executed for all descriptors for which transmission requests have been made."

If all descriptors requested to be transmitted have not been determined (NO in S1600), the descriptor execution management unit 13 selects one of the undetermined descriptors as a "target descriptor" from among the descriptors requested to be transmitted. do. Then, the descriptor execution management unit 13 acquires the priority NPR, transmission time NST, etc. of the selected target descriptor (S1700). The descriptor execution management unit 13 then executes the processes from S1300 onwards.

That is, the descriptor execution management unit 13 checks whether there is any descriptor for which the processing from S1200 (or S1700) to S1500 has not been executed among the descriptors for which a transmission request has been made. If there is a descriptor for which the processes from S1200 (or S1700) to S1500 have not been executed, the descriptor execution management unit 13 executes the processes from S1700 to S1500 for that descriptor.

Finally, the descriptor execution management unit 13 selects the descriptor corresponding to the current transmission time CST, current priority CPR, and current transfer time CRT as the descriptor to be executed (read) at the current time CT (S1800).

(Detailed example of update process)
FIG. 16 shows an example of the update process (S1500) illustrated in FIG. 15 when the priority NPR of the target descriptor is the same as the current priority CPR and when the priority NPR of the target descriptor is higher than the current priority CPR. FIG.

(Example of update processing when the priority of the target descriptor is the same as the current priority)
If the priority NPR of the target descriptor is the same as the current priority CPR, the descriptor execution management unit 13 executes the update process illustrated in FIG. 16(A). That is, the descriptor execution management unit 13 first determines whether "the transmission time NST of the target descriptor is earlier than the current transmission time CST" (S1511).

If the transmission time NST of the target descriptor is earlier than the current transmission time CST (YES in S1511), the descriptor execution management unit 13 updates the values of the current transmission time CST, current priority CPR, and current transfer time CRT. (S1512). Specifically, the descriptor execution management unit 13 updates the value of the current transmission time CST with the value of the transmission time NST of the target descriptor. Further, the descriptor execution management unit 13 updates the value of the current priority CPR with the value of the priority NPR of the target descriptor. Furthermore, the descriptor execution management unit 13 updates the value of the current transfer time CRT with the value of the transfer time NRT of the transmission data corresponding to the target descriptor.

In the determination of S1511, if "current transmission time CST=0", the descriptor execution management unit 13 determines "YES in S1511" and moves to the next process, that is, executes S1512.

If the transmission time NST of the target descriptor is later than the current transmission time CST, or if the current transmission time CST and the transmission time NST of the target descriptor are the same (NO in S1511), the descriptor execution management unit 13 ends the update process. do.

(Example of update processing when the priority of the target descriptor is higher than the current priority)
If the priority NPR of the target descriptor is higher than the current priority CPR, the descriptor execution management unit 13 executes the update process illustrated in FIG. 16(B). That is, the descriptor execution management unit 13 first determines whether "the transmission time NST of the target descriptor is earlier than the current transmission time CST, or whether the current transmission time CST and the transmission time NST of the target descriptor are the same". (S1521).

If the transmission time NST of the target descriptor is earlier than the current transmission time CST, or if they are the same (YES in S1521), the descriptor execution management unit 13 updates the current variable (S1525). Specifically, the descriptor execution management unit 13 updates the value of the current transmission time CST with the value of the transmission time NST of the target descriptor. Further, the descriptor execution management unit 13 updates the value of the current priority CPR with the value of the priority NPR of the target descriptor. Furthermore, the descriptor execution management unit 13 updates the value of the current transfer time CRT with the value of the transfer time NRT of the transmission data corresponding to the target descriptor.

In the determination of S1521, if "current transmission time CST=0", the descriptor execution management unit 13 determines "YES in S1521" and moves to the next process, that is, executes S1525.

If the transmission time NST of the target descriptor is later than the current transmission time CST (NO in S1521), the descriptor execution management unit 13 determines the end time when the target data is transferred after the current transfer execution (that is, the scheduled total time ERT). ) is calculated (S1523). That is, the descriptor execution management unit 13 calculates "scheduled total time ERT=current time CT+current transfer time CRT+transfer time NRT of target descriptor".

The descriptor execution management unit 13 determines whether "transmission time NST of the target descriptor < scheduled total time ERT", that is, determines "whether the transmission time NST of the target descriptor is smaller (earlier) than the scheduled total time ERT". (S1524).

If the transmission time NST of the target descriptor is earlier than the scheduled total time ERT (YES in S1524), the descriptor execution management unit 13 updates the current variable (S1525). If the transmission time NST of the target descriptor is the same as the scheduled total time ERT, or if the transmission time NST of the target descriptor is greater (later) than the scheduled total time ERT (NO in S1524), the descriptor execution management unit 13 ends the update process. do.

Here, in (B) of FIG. 16, since the priority NPR of the target descriptor is higher than the current priority CPR, the target descriptor corresponds to the "high priority descriptor in FIG. 6", and the current descriptor corresponds to the "low priority descriptor in FIG. 6". descriptor”. Further, in FIG. 16(B), the transmission time NST corresponds to the "transmission time TT (high priority) specified by the high priority descriptor" in FIG.

Therefore, S1524 in FIG. 16(B) performs the same determination as S130 in FIG. That is, if YES in S1524, the descriptor execution management unit 13 updates the current descriptor so that the target descriptor corresponding to the high priority descriptor is selected as the descriptor to be executed at the current time CT.

If NO in S1524, the descriptor execution management unit 13 does not update the current descriptor so that the current descriptor corresponding to the low priority descriptor is selected as the descriptor to be executed at the current time CT.

(Example of update processing when the priority of the target descriptor is lower than the current priority)
FIG. 17 is a flow diagram illustrating an example of the update process (S1500) illustrated in FIG. 15 when the priority NPR of the target descriptor is lower than the current priority CPR. As shown in FIG. 17, the descriptor execution management unit 13 first determines whether "the transmission time NST of the target descriptor is earlier than the current transmission time CST" (S1531).

If the transmission time NST of the target descriptor is earlier than the current transmission time CST (YES in S1531), the descriptor execution management unit 13 determines the end time when the target data is transferred after the current transfer execution (that is, the scheduled total time ERT). ) is calculated (S1523). That is, the descriptor execution management unit 13 calculates "scheduled total time ERT=current time CT+current transfer time CRT+transfer time NRT of target descriptor".

The descriptor execution management unit 13 determines whether "current transmission time CST < scheduled total time ERT", that is, determines "whether current transmission time CST is smaller (earlier) than scheduled total time ERT" (S1533). . If the current transmission time CST is earlier than the scheduled total time ERT (YES in S1533), the descriptor execution management unit 13 ends the update process.

If the current transmission time CST is the same as the scheduled total time ERT, or if the current transmission time CST is greater (later) than the scheduled total time ERT (NO in S1533), the descriptor execution management unit 13 updates the current variable (S1534) .

Here, in FIG. 17, since the priority NPR of the target descriptor is lower than the current priority CPR, the target descriptor corresponds to the "low priority descriptor in FIG. 6", and the current descriptor corresponds to the "high priority descriptor in FIG. 6". do. Further, in FIG. 17, the current transmission time CST corresponds to the "transmission time TT (high priority) defined by the high priority descriptor" in FIG.

Therefore, S1533 in FIG. 17 performs the same determination as S130 in FIG. That is, if YES in S1533, the descriptor execution management unit 13 does not update the current descriptor so that the current descriptor corresponding to the high priority descriptor is selected as the descriptor to be executed at the current time CT.

If NO in S1533, the descriptor execution management unit 13 updates the current descriptor so that the target descriptor corresponding to the low priority descriptor is selected as the descriptor to be executed at the current time CT.

§4. Modified example (About network configuration example)
In the control system 0 illustrated in FIG. 2, a plurality of networks 3 are connected to the PLC 1 via the network hub 2. However, in the control system 0, one network 3 is connected to the PLC 1 without going through the network hub 2, and for example, the PLC 1 and one or more network devices are connected to each other in a single-stroke manner so that they can communicate with each other. You can.

The present invention is not limited to the embodiments described above, and various modifications can be made within the scope of the claims, and embodiments obtained by appropriately combining technical means disclosed in different embodiments. are also included within the technical scope of the present invention.

10 Communication controller (communication control equipment)
20 Main memory 162 Buffer (transmission buffer)
131 Selection section 132 Reading section CT Current time ERT Scheduled total time JT Judgment time P Priority (execution priority)
RT Transfer time S20 Selection step S30 Reading step TT Transmission time (scheduled transmission time)

Claims (8)

A communication control device that transfers data from a main memory to a transmission buffer according to a read descriptor, and transmits the data transferred to the transmission buffer,
a selection unit that selects a descriptor to read from among the plurality of descriptors based on both a scheduled transmission time and an execution priority defined in each of the plurality of descriptors;
A communication control device comprising: a reading section that reads the descriptor selected by the selection section. A communication control device that transfers data from a main memory to a transmission buffer according to a read descriptor, and transmits the data transferred to the transmission buffer,
a selection unit that selects a descriptor to be read from among the plurality of descriptors based on at least one of a scheduled transmission time and an execution priority defined in each of the plurality of descriptors;
a reading unit that reads the descriptor selected by the selection unit;
Equipped with
When the execution priority of a certain descriptor among the plurality of descriptors is higher than the execution priority of another descriptor, the selection unit:
(A) Transfer time required to transfer data corresponding to the certain descriptor from the main memory to the transmission buffer and transfer data corresponding to the another descriptor from the main memory to the transmission buffer at the current time; (B) compare the scheduled transmission time of the certain descriptor with the scheduled total time, which is the time obtained by adding the transfer time required to transfer
If the scheduled transmission time of the certain descriptor is later than the scheduled total time, selecting the other descriptor in preference to the certain descriptor;
If the scheduled transmission time of the certain descriptor is before the scheduled total time, the communication control device selects the certain descriptor with priority over the other descriptor. A communication control device that transfers data from a main memory to a transmission buffer according to a read descriptor, and transmits the data transferred to the transmission buffer,
a selection unit that selects a descriptor to read from among the plurality of descriptors based on at least one of a scheduled transmission time and an execution priority defined in each of the plurality of descriptors;
a reading section that reads the descriptor selected by the selection section;
Equipped with
Judgment time is preset,
The reading unit is a communication control device that reads the descriptor after the determination time has elapsed from the scheduled transmission time of the descriptor. A communication control device that transfers data from a main memory to a transmission buffer according to a read descriptor, and transmits the data transferred to the transmission buffer,
a selection unit that selects a descriptor to be read from among the plurality of descriptors based on at least one of a scheduled transmission time and an execution priority defined in each of the plurality of descriptors;
a reading unit that reads the descriptor selected by the selection unit;
Equipped with
The transmission buffer is
a normal transmission buffer in which the data corresponding to the descriptors are stored in the order of the descriptors read by the reading unit;
The reading unit reads the descriptor corresponding to the data stored in the normal transmission buffer after the selection unit selects the descriptor and before the data stored in the normal transmission buffer is transmitted. a special transmission buffer in which the data corresponding to the descriptor having a higher execution priority than the descriptor corresponding to the data stored in the normal transmission buffer is stored. device. A control method for a communication control device that transfers data from a main memory to a transmission buffer according to a read descriptor, and transmits the data transferred to the transmission buffer, the method comprising:
a selection step of selecting a descriptor to be read from among the plurality of descriptors based on both the scheduled transmission time and the execution priority defined in each of the plurality of descriptors;
a reading step of reading the descriptor selected in the selecting step. A control method for a communication control device that transfers data from a main memory to a transmission buffer according to a read descriptor, and transmits the data transferred to the transmission buffer, the method comprising:
a selection step of selecting a descriptor to be read from among the plurality of descriptors based on at least one of a scheduled transmission time and an execution priority defined in each of the plurality of descriptors;
a reading step of reading the descriptor selected in the selection step;
including;
If the execution priority of a certain descriptor among the plurality of descriptors is higher than the execution priority of another descriptor, in the selection step,
(A) Transfer time required to transfer data corresponding to the certain descriptor from the main memory to the transmission buffer and transfer data corresponding to the another descriptor from the main memory to the transmission buffer at the current time; (B) compare the scheduled transmission time of the certain descriptor with the scheduled total time, which is the time obtained by adding the transfer time required to transfer
If the scheduled transmission time of the certain descriptor is later than the scheduled total time, selecting the other descriptor in preference to the certain descriptor;
If the scheduled transmission time of the certain descriptor is before the scheduled total time, the certain descriptor is selected with priority over the other descriptor. A control method for a communication control device that transfers data from a main memory to a transmission buffer according to a read descriptor, and transmits the data transferred to the transmission buffer, the method comprising:
a selection step of selecting a descriptor to be read from among the plurality of descriptors based on at least one of a scheduled transmission time and an execution priority defined in each of the plurality of descriptors;
a reading step of reading the descriptor selected in the selection step;
including;
Judgment time is preset,
In the reading step, the control method reads the descriptor after the determination time has elapsed from the scheduled transmission time of the descriptor. A control method for a communication control device that transfers data from a main memory to a transmission buffer according to a read descriptor, and transmits the data transferred to the transmission buffer, the method comprising:
a selection step of selecting a descriptor to be read from among the plurality of descriptors based on at least one of a scheduled transmission time and an execution priority defined in each of the plurality of descriptors;
a reading step of reading the descriptor selected in the selection step;
including;
The transmission buffer is
a normal transmission buffer in which the data corresponding to the descriptors are stored in the order of the descriptors read in the reading step;
After the descriptor corresponding to the data stored in the normal transmission buffer is selected in the selection step and before the data stored in the normal transmission buffer is transmitted, the descriptor is read in the reading step. a special transmission buffer in which the data corresponding to the descriptor having a higher execution priority than the descriptor corresponding to the data stored in the normal transmission buffer is stored.
control methods including.

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