JP2021141537A - Communication control apparatus and method for controlling communication control apparatus - Google Patents

Abstract

To reduce a processing load on a processor while reducing a mounting size.SOLUTION: A communication controller (10) selects a transmission descriptor to be preferentially read based on at least one of a transmission time (TT) and priority (P) that are defined in each of a plurality of transmission descriptors.SELECTED DRAWING: Figure 1

Description

The present invention relates to a communication control device or the like 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 for industrial control devices such as PLCs (Programmable Logic Controllers; hereinafter also referred to as PLCs) for distributing the load on the processor. For example, Patent Document 1 below includes a processor composed of a plurality of cores, a plurality of queues, and a plurality of communication ports, associates each queue with each core, and displays the processing result in each core in each core. The controller to be stored in each queue corresponding to is disclosed. In the controller of Patent Document 1, the same number of queues as the number of cores is provided, and the same number of communication ports as the number of queues are provided, and each queue corresponding to each core outputs the processing result in each core, etc. We are trying to reduce the load on the processor by controlling.

Japanese Unexamined Patent Publication No. 2008-134775

However, in the above-mentioned conventional technique, since the transmission queue is divided for each network segment, there is a problem that when the number of network segments increases, a plurality of transmission queues are required to match the number of network segments, which makes it difficult to realize. That is, considering the semiconductor of the network interface card (NIC), the gate usage of the FPGA (Field-programmable gate array), and the like, there is a limit to the number of transmission queues that can be increased.

One aspect of the present invention is to realize a communication control device capable of reducing the processing load of software (processor) while suppressing the mounting size.

In order to solve the above problems, the communication control device according to one aspect of the present invention transfers data from the main memory to the transmission buffer according to the 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 a plurality of the descriptors based on at least one of a scheduled transmission time and an execution priority defined in each of the plurality of descriptors, and the above-mentioned It includes a reading unit that reads the descriptor selected by the selection unit.

According to the above configuration, the communication control device reads a descriptor from 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 from the plurality of descriptors to be read based on at least one of the scheduled transmission time and the 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 mounting size can be reduced.

Further, the communication control device controls the output of the processing result by the software (processor), specifically, the transmission order of the data by controlling the reading order of the plurality of descriptors. That is, the software can treat the communication control device as one hardware having a plurality of transmission queues for managing "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 an effect that the processing load of the software can be reduced while suppressing the mounting size.

Regarding the communication control device according to one aspect of the present invention, when the execution priority of one descriptor among a plurality of descriptors is higher than the execution priority of another descriptor, the selection unit is (A). At the current time, the transfer time required to transfer the data corresponding to the certain descriptor from the main memory to the transmission buffer and the data corresponding to the other descriptor are transferred from the main memory to the transmission buffer. The scheduled total time, which is the time obtained by adding the transfer time required for the data, is compared with (B) the scheduled transmission time of the descriptor, and the scheduled transmission time of the descriptor is the scheduled total time. After that, the other descriptor is selected in preference to the certain descriptor, and when the scheduled transmission time of the certain descriptor is before the scheduled total time, the descriptor is given priority over the other descriptor. Certain descriptors 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 has the scheduled total time and the transmission schedule of the certain descriptor. Compare with time. Then, when 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, when 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, when the descriptor to be read is selected based only on the execution priority specified in each of the plurality of descriptors, the descriptor having the lower execution priority is always read after the descriptor having the higher execution priority. Will be.

However, when the scheduled transmission time of the other descriptor, which has a lower execution priority than the certain descriptor, is sufficiently earlier than the scheduled transmission time of the certain descriptor, the descriptor read order is determined only according to the execution priority. Is not always appropriate.

For example, even 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 transmitted before the scheduled transmission time of the certain transmission descriptor. It may be possible to transfer to the main memory. 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 transmission descriptor.

Further, when a descriptor to be read is selected based only on the scheduled transmission time specified in each of the plurality of descriptors, the descriptor having the late scheduled transmission time is always read after the descriptor having the early scheduled transmission time. It will be.

However, when 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 descriptor reading order is determined only according to the scheduled transmission time. Is not always 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 sent 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 the other descriptor is read (executed), that is, the certain descriptor should be read before the other transmit descriptor. be.

The communication control device compensates for the above-mentioned deficiencies of each of the determination of the descriptor reading order according to the execution priority only and the determination of the descriptor reading order according only to 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 performs 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 an effect that the descriptor to be read can be appropriately selected as compared with the method of selecting the descriptor to be read according to only one of the execution priority and the scheduled transmission time.

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

According to the above configuration, the communication control device reads the descriptor after the time is set back from the scheduled transmission time of the descriptor to the determination time.

Here, when another descriptor whose scheduled transmission time is closer to the current time than the scheduled transmission time of the certain descriptor is generated after reading a certain descriptor, the following problem occurs. That is, there arises a problem that the data corresponding to the certain descriptor becomes an obstacle 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 they are stored. That is, if the data corresponding to the certain descriptor is stored before the data corresponding to the other descriptor, the data corresponding to the certain descriptor must be transmitted before the data corresponding to the other descriptor is transmitted. No data is sent. Then, the data corresponding to the certain descriptor is not transmitted until the scheduled transmission time of the certain descriptor is reached. However, since the scheduled transmission time of the certain descriptor is later than the scheduled transmission time of the other descriptor, it is not possible 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 time is set back from the scheduled transmission time of the descriptor to the determination time. That is, the communication control device is said so that the certain descriptor is not 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. Adjust the read time of a descriptor. Specifically, the communication control device reads the descriptor after the time is set back from the scheduled transmission time of the descriptor to the determination time.

Therefore, the communication control device can prevent the 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 descriptor. It has the effect of.

In the communication control device according to one aspect of the present invention, the transmission buffer is stored in the normal transmission buffer in which the data corresponding to the descriptor is stored and the normal transmission buffer in the order of the descriptor read by the reading unit. It is a descriptor read by the reading unit between the time when the selecting unit selects the descriptor corresponding to the data being stored and the time when the data stored in the normal transmission buffer is transmitted. It may include a special transmit 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 transmit 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 usually stores the data corresponding to the read descriptor in the order of the read descriptor in the normal transmission buffer.

The communication control device is new during "from the selection of the descriptor corresponding to the data stored in the normal transmission buffer to the transmission of the data stored in the normal transmission buffer". When the descriptor is read, the following judgment is executed. 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.

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

Here, between the time when the selection unit selects a certain descriptor and the time when the data corresponding to the certain descriptor is transmitted, another descriptor having a higher execution priority than the certain descriptor is read. The part may read. In such a case, if there is only one transmit buffer, the data corresponding to the other descriptor must be stored in the only transmit buffer after the data corresponding to the one descriptor. .. As a result, it becomes impossible to transmit the data corresponding to the other descriptor before the 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 to be transmitted is generated with priority over the data stored in the normal transmission buffer, the communication control device stores such data in the special transmission buffer.

Therefore, the communication control device preferentially transmits data to be transmitted over the data corresponding to the descriptor, which is generated from the selection of the descriptor to the transmission of the data corresponding to the descriptor. It has the effect of being able to send with priority.

In order to solve the above problems, the control method according to one aspect of the present invention is a communication control in which data is transferred from the main memory to a transmission buffer according to a read descriptor and the data transferred to the transmission buffer is transmitted. A selection step of selecting a descriptor to be read from a plurality of the descriptors based on at least one of a scheduled transmission time and an execution priority defined in each of the plurality of descriptors, which is a control method of the device. , A read step to read the descriptor selected in the selection step.

According to the above configuration, the control method selects a descriptor to be read from a plurality of the descriptors based on at least one of a scheduled transmission time and an execution priority defined in each of the plurality of descriptors. do. Then, 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 from the plurality of descriptors to be read based on at least one of the scheduled transmission time and the execution priority of each of the plurality of descriptors.

Therefore, the communication control device 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 mounting size of the communication control device that executes the control method can be reduced. ..

In addition, 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. That is, the software can treat the communication control device as one hardware having a plurality of transmission queues for managing "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 an effect that the processing load of the software can be reduced while suppressing the mounting size of the communication control device that executes the control method.

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

It is a figure which shows the main part structure of the PLC including the communication controller which concerns on Embodiment 1 of this invention. It is a figure which shows the outline of the control system including PLC of FIG. It is a flow diagram explaining the outline of the process executed by the communication controller which concerns on Embodiment 1 of this invention. In Case 1, it is a figure explaining the situation which occurs when the descriptor to be read first is selected based only on priority. In Case 2, it is a figure explaining the situation which occurs when the descriptor to be read first is selected based only on the transmission time. It is a flow chart which shows an example of the selection process which the communication controller which concerns on Embodiment 1 of this invention executes in consideration of priority and transmission time. It is a figure explaining the descriptor which the communication controller which concerns on Embodiment 1 of this invention selects by executing the flow illustrated in FIG. FIG. 6 is a diagram showing a specific processing example when the flow illustrated in FIG. 6 is executed in Case 1. FIG. 6 is a diagram showing a specific processing example when the flow illustrated in FIG. 6 is executed in Case 2. It is a table which organized the information used when the communication controller which concerns on Embodiment 1 of this invention calculates the transfer time of a certain transmission data. It is a figure explaining the situation which occurs when the determination time is not provided in case 3. FIG. 3 is a diagram showing a specific processing example realized in the case 3 when the communication controller according to the first embodiment of the present invention is provided with a determination time. It is a flow chart which shows the processing example which a CPU and a requester execute. It is a flow diagram which shows the processing example which the descriptor execution management unit, the BUF management unit and the like execute. It is a flow chart which shows an example of the selection process illustrated in (A) of FIG. FIG. 5 is a flow chart showing an example of the update process 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. 5 is a flow chart showing an example in which the priority of the target descriptor is lower than the current priority in the update process illustrated in FIG. 15.

[Embodiment 1]
Hereinafter, embodiments according to one aspect of the present invention (hereinafter, also referred to as “the present embodiment”) will be described with reference to the drawings. The same or corresponding parts in the drawings are designated by the same reference numerals, and the description thereof will not be repeated. In the present embodiment, the communication controller 10 included in the PLC (Programmable Logic Controller) 1 that controls the control target of the machine, equipment, or the like will be described as a typical example of the communication control device.

In the following description, "n" may indicate an integer of "1" or more, "buffer" may be abbreviated as "BUF", and "descriptor memory" for storing a transmission descriptor may be 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. When it is not necessary to distinguish each of the first buffer 162 (0), the second buffer 162 (1), and the nth buffer 162 (n-1), it is simply 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 nth descriptor memory 14 (n-1) is abbreviated as "TXn-1". May be abbreviated as. When it is not necessary to distinguish each of the first descriptor memory 14 (0), the second descriptor memory 14 (1), and the nth descriptor memory 14 (n-1), it is simply "descriptor memory 14" or "TX". May be.

Further, when it is not necessary to distinguish each of the first requester 15 (0), the second requester 15 (1), and the nth requester 15 (n-1), it may be simply referred to as "requester 15". ..

§1. Application Example In order to facilitate understanding of the communication controller 10 (communication control device) according to one aspect of the present invention, first, an example of a situation in which the present invention is applied is specifically a PLC1 including a communication controller 10. The outline of the control system 0 including the above will be described with reference to FIG.

(Overview of control system)
FIG. 2 is a diagram showing an outline of the control system 0. The control system 0 includes a PLC 1, a network hub 2, and networks 3 (1) and 3 (2), each of which is connected to the PLC 1 via the network hub 2. Hereinafter, when it is not necessary to distinguish between the network 3 (1) and the network 3 (2), it 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 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 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), are used for one network port of PLC1 (that is, transmission port 18 in FIG. 1). Existing.

Here, both networks 3 (1) and 3 (2) may be control networks, that is, all networks 3 communicating with PLC1 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. That is, with respect to the network 3 communicating with the PLC 1, the control network and the data network may be used. It may be mixed.

For example, when the network 3 is a control network, the PLC 1 is a control device that controls the input device and the output device in the production equipment, and the network device is, for example, an input device and an output device in the production equipment. be. The PLC1 and the network device transmit and receive IN data and OUT data (hereinafter referred to as "IO data") by cyclically communicating with each other via the network 3, and the PLC1 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 PLC1 is a master device (master device that manages data transmission) and the network device is a slave device.

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

In the following, an example in which communication between PLC1 and a network device in FIG. 2 (hereinafter, also referred to as “network communication”) conforms to the Ethernet standard will be described. Further, it is assumed that the CPU 30 and the communication controller 10 are communicably connected by PCIe (Peripheral Component Interconnect Express).

Note that FIG. 2 illustrates a control system 0 in which a plurality of networks 3 are connected to the PLC 1 via the network hub 2. However, in the control system 0, the plurality of networks 3 are connected to the PLC 1 via the network hub 2. It is not essential to connect with. In the control system 0, one network 3 (particularly 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 PLC1 which is a master device and one or more network devices, each of which is a slave device, may be communicably connected in a one-stroke format.

(Outline of processing executed by the communication controller according to this embodiment)
In order to facilitate understanding of the communication controller 10 whose details will be described below with reference to FIG. 1 and the like, the processes executed by the communication controller 10 are organized as follows.

That is, when the communication controller 10 receives a plurality of transmission requests (that is, execution requests of a plurality of transmission descriptors) from the software (that is, the CPU 30) substantially at the same time, 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 (particularly, the selection unit 131) sets the "transmission time TT" and the "priority P specified by the software" for each of the plurality of transmission descriptors (descriptors) to be executed. get. Then, the descriptor execution management unit 13 selects the descriptor to be executed, that is, the descriptor to be read, using the acquired "transmission time TT and priority P of each of the plurality of descriptors". Although the 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 the plurality of descriptors" when selecting the descriptor to be read.

Here, in order to reduce the processing load of the CPU, it is known that the configuration of managing the "transmission order and actual transmission time (actual transmission time RTT) of the transmission data" by a NIC or the like configured by a logic circuit by hardware is known. Has been done. The "actual transmission time RTT" is the time when the transmission data is actually transmitted, and the transmission in which the actual transmission time RTT matches 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 has a transmit BUF. Then, in an example of such a NIC, a "transmission queue including DMAC and transmission BUF" is provided for each communication network for which "transmission order and actual transmission time RTT of transmission data" should be managed. ..

However, if the NIC is provided with a "transmission queue equipped with DMAC and transmission BUF" for each communication network for which "transmission order and actual transmission time RTT of transmission data" should be managed, the following problems occur. .. That is, as the number of communication networks to be managed increases, the number of "transmission queues including DMAC and transmission BUF" also increases, so that the mounting size of the NIC increases.

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

For example, the communication controller 10 illustrated in FIG. 1 includes "two" buffers 162 for temporarily holding the transmission data read from the main memory 20 before transmission, but the communication controller 10 includes the communication controller 10. The number of buffers 162 provided may be "one". That is, since the communication controller 10 executes the plurality of descriptors to be executed one by one in a desired order, the communication controller 10 temporarily holds the buffer 162 for transmitting data by "one". All you have to do is prepare. However, by providing "two" or more buffers 162, the communication controller 10 corresponds to another descriptor when another descriptor having a higher priority P is executed after executing a certain 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, since the communication controller 10 can execute a plurality of descriptors to be executed one by one in a desired order, data exchange between the main memory 20 and the buffer 162 is realized. It is sufficient that "one" DMAC12 is provided.

Therefore, the communication controller 10 does not need to include a plurality of "transmission queues including the DMAC and the transmission BUF", so that the mounting size can be reduced. In particular, even if the number of communication networks (networks 3) for which "transmission order and actual transmission time RTT of transmission data" should be managed increases, the communication controller 10 can suppress an increase in the mounting size.

The details will be described later with reference to FIG. 1, but the communication controller 10 includes "one" transmission port 18 and "one" DMAC12. The communication controller 10 is provided with a plurality of transmission queues for managing "transmission order and actual transmission time RTT of transmission data" for "one" transmission port 18 and "one" DMAC12. .. 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 is provided. "One" is provided. The communication controller 10 includes a plurality of transmission queues for managing "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 the transmission data" in the same manner as having a plurality of transmission queues while suppressing the mounting size.

For example, the communication controller 10 is composed of a logic circuit made of hardware such as FPGA (Field-Programmable gate array) or ASIC (Application Specific Integrated Circuit). In that case, the software (that is, the CPU 30) can handle the communication controller 10 as hardware having a plurality of transmission queues for managing "transmission order and actual transmission time RTT of transmission data". Therefore, by configuring the communication controller 10 with a logic circuit by hardware, the communication controller 10 that manages the "transmission order and actual transmission time RTT of the transmission data" reduces the processing load of the 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 transmits the transferred data to the buffer 162. It is a device.

The communication controller 10 includes a selection unit 131 and a reading unit 132. The selection unit 131 of the plurality of transmission descriptors is based on at least one of the "transmission time TT (scheduled transmission time)" and the "priority P (execution priority)" defined in each of the plurality of transmission descriptors. Select the transmit descriptor to read from the list. That is, the selection unit 131 selects a transmission descriptor to be executed from 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. .. 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 be read from 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. Then, the communication controller 10 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 the plurality of transmission descriptors based on at least one of the transmission time TT and the 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 mounting size can be reduced.

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

Therefore, the communication controller 10 has an effect that the processing load of the software can be reduced while suppressing the mounting size.

In the communication controller 10, the buffer 162 is roughly classified into a normal transmission buffer and a special transmission buffer. In the normal transmission buffer, data corresponding to the transmission descriptor is stored in the order of the transmission descriptors read by the reading unit 132. In the special transmission buffer, the data corresponding to the "descriptor that satisfies both of the following two conditions" is stored. Condition 1 is a descriptor read by the reading unit 132 during "from the selection of the transmission descriptor corresponding to the data normally stored in the transmission buffer to the transmission of the data". There is. " Condition 2 is "higher priority P than the transmit descriptor corresponding to the data normally stored in the transmit buffer".

At least one of the first buffer 162 (0), the second buffer 162 (1), ..., The nth buffer 162 (n-1) is used as a special transmission buffer, and the other buffers 162 are normally transmitted. It may 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 the data corresponding to the read transmission descriptor in the order of the read transmission descriptor in the normal transmission buffer.

The communication controller 10 reads a new descriptor during "from the selection of the transmission descriptor corresponding to the data stored in the normal transmission buffer to the transmission of the data stored in the normal transmission buffer". And, the following judgment is executed. 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.

Then, when the priority P of the new descriptor is higher, the communication controller 10 stores the data corresponding to the new descriptor in the special transmission buffer. On the other hand, when the priority P of the new descriptor is lower or the priority P of both is the same, the communication controller 10 stores the data corresponding to the new descriptor in the normal transmission buffer. do.

Here, between the time when the selection unit 131 selects a certain transmission descriptor and the time when the data corresponding to the certain transmission descriptor is transmitted, another descriptor having a higher priority P than the certain transmission descriptor is selected. The reading unit 132 may read. In such a case, if there was only one transmit buffer, the data corresponding to that other descriptor would have to be stored in the only transmit buffer after the data corresponding to that one transmit descriptor. No. As a result, it becomes impossible to transmit the data corresponding to the other descriptor before the data corresponding to the one 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 to be transmitted is generated with priority over the data stored in the normal transmission buffer, the communication controller 10 stores such data in the special transmission buffer.

Therefore, the communication controller 10 gives priority to the data to be transmitted with priority over the data corresponding to the certain transmission descriptor generated until the data corresponding to the certain transmission descriptor is transmitted after the selection of the certain transmission descriptor. It has the effect of being able to send.

§2. Configuration Example The communication controller 10 and the PLC1 including the communication controller 10 whose outline has been described so far will be described in detail with reference to FIG.

FIG. 1 is a diagram showing a configuration example of PLC1. 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 PLC1 may further include a non-volatile memory (not shown), a USB connector for connecting an external device and the PLC1, and the like. The communication controller 10, the main memory 20, the CPU 30, and the non-volatile memory are respectively 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 CPU 30 includes one or more CPU cores and a network control unit as a hardware configuration.
The CPU 30 executes various arithmetic processes and stores the data generated as the execution result in the main memory 20 as transmission data. Further, with respect to the data stored in the main memory 20 as transmission data, the CPU 30 transmits the descriptor data that defines the priority P of the transmission data, the transmission time TT, the address in the main memory 20, the data size, and the like to the main memory 20. Store. The descriptor data that defines the priority P of the transmission data, the transmission time TT, the address in the main memory 20, the data size, and the like may be abbreviated as "transmission descriptor" or simply "descriptor".

The "transmission time TT" of the transmission data is given by the CPU 30 and indicates the time when the communication controller 10 transmits the transmission data to the network 3, that is, the transmission data should be transmitted to the network 3. Indicates the scheduled transmission time. Further, the "priority P" of the transmission data is given by the CPU 30, and indicates the high necessity of "transmitting the transmission data at the" transmission time TT "". For example, "the transmission data is transmitted with a transmission cycle". It shows the high need to "maintain and periodically transmit to network 3".

Here, in general, an industrial controller such as PLC1 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 a communication priority CP of the unit group may be set for the unit group including the one or more network devices.

Then, the communication priority CP and the priority P may be associated with each other. Further, the communication priority CP of a certain unit group (eg, unit group U1) is higher than the communication priority CP of another unit group (eg, unit group U2), that is, the communication cycle of the certain unit group. It may mean that the need to maintain is higher than that of the other unit group. Furthermore, the fact that the communication priority CP of a certain unit group (eg, unit group U1) is higher than the communication priority CP of another unit group (eg, unit group U2) means that the communication cycle of the certain unit group However, it may mean that it is earlier (shorter) than the communication cycle of the other unit group.

For example, "periodic communication performed by PLC1 (particularly, the communication controller 10) with one network device" is more than "periodic communication performed by PLC1 with another network device". It may be necessary to maintain the communication cycle. In such a case, the communication priority CP of "periodic communication executed with the certain network device" is the communication of "periodic communication executed with the other network device". Higher than priority CP.

Further, "periodic communication executed by PLC1 (particularly, the communication controller 10) with a certain network device" is more than "periodic communication executed by PLC1 with another network device". The communication cycle may be short (fast). In such a case, the communication priority CP of "periodic communication executed with the certain network device" is the communication of "periodic communication executed with the other network device". Higher than priority CP.

Then, when the communication priority CP of "periodic communication executed with a certain network device" is higher than the communication priority CP of "periodic communication executed with another network device", the CPU 30 Gives priority P to the transmitted data as follows. That is, the CPU 30 assigns the "transmission data destined for the certain network device" a priority P higher than the priority P assigned to the "transmission data destined for the other network device".

The main memory 20 is a storage means of the PLC 1, and for example, data (transmission data) transmitted by the PLC 1 (particularly, the communication controller 10) to the network 3 is stored. The main memory 20 is a volatile storage area (RAM), and in addition to storing transmission data "generated by various arithmetic processes by the CPU 30 and transmitted to the network 3", the CPU 30 is used after the power is turned on to the PLC 1. 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 a main memory 20, for example, a DRAM (Dynamic Random Access Memory), a SRAM (Static Random Access Memory), or the like can be used.

In the main memory 20 illustrated in FIG. 1, the descriptor data (transmission descriptor) corresponding to the transmission data is stored together with the transmission data. The transmission descriptor includes information indicating the transmission time TT, priority P, data size, and the like of the corresponding transmission data.

The PLC1 may include a non-volatile memory that non-volatilely holds data such as various programs and parameters. These data stored in the non-volatile memory are copied to the main memory 20 so that the CPU 30 can access them, if necessary. As such a non-volatile memory, a semiconductor memory such as a flash memory can be used. 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), or the like can 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 composed of a logic circuit made of hardware such as an FPGA (Field-Programmable gate array) or an ASIC (Application Specific Integrated Circuit). The communication controller 10 is configured to be capable of transmitting and receiving 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, for example, "transmission order and actual transmission of transmission data". Control the "time RTT". The communication controller 10 provides, for example, the functions of the physical layer and the data link layer in the network 3. That is, the communication controller 10 controls the transmission of the transmission data and the reception of the received data in accordance with the standard to which the network 3 conforms. Specifically, the communication controller 10 transfers the data (transmission data) stored in the main memory 20 to the buffer 162 in the own device, and the transmission data stored in the buffer 162 is connected to the network 3. Send to your network device.

The communication controller 10 transmits transmission data according to the contents specified in the transmission descriptor, and for example, transmits the transmission data corresponding to the transmission descriptor at the transmission time TT specified in the transmission descriptor. The fact that the communication controller 10 transmits the transmission data at the transmission time TT set for the transmission data (that is, the transmission time TT specified by the transmission descriptor corresponding to the transmission data) is also referred to as "time transmission". Refer to.

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

Although the details will be described later, in the PLC 1, the data (transmission data) stored in the main memory 20 is transmitted to the network 3 and the actual transmission by the communication controller 10 configured by the logic circuit by the hardware instead of the CPU 30. Control the time RTT. Therefore, the PLC 1 can control the transmission order of the transmission data to the network 3 and the actual transmission time RTT by the communication controller 10 configured by the logic circuit by the hardware without increasing the processing load of the CPU 30. Play the effect of.

The communication controller 10 illustrated in FIG. 1 has IF11, DMAC12, descriptor execution management unit 13, two or more descriptor memories 14, two or more requesters 15, BUF management unit 16, arbitration unit 17, and the arbitration unit 17, as functional blocks. A transmission port 18 is provided.

The IF 11 is an interface for the communication controller 10 (particularly, the DMAC 12) to communicate with each of the main memory 20 and the CPU 30.

The DMAC 12 performs data exchange between the main memory 20 and each of the descriptor memory 14 and the buffer 162. For example, the DMAC 12 reads the 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 buffers the acquired data. Store in 162. For example, the DMAC 12 acquires the transmission data specified by the “address of the main memory 20” and the “data size of the transmission data” defined in the transmission descriptor from the main memory 20. 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 transmission data from the main memory 20 to the buffer 162 according to "a transmission descriptor stored in the descriptor memory 14 and a transmission descriptor read (executed) by the descriptor execution management unit 13". do.

When the descriptor execution management unit 13 receives 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 requester 15 notifies that "there is a transmit descriptor to be executed (read)", the descriptor execution management unit 13 reads (executes) the transmit descriptor with reference to the descriptor memory 14. ). Then, the descriptor execution management unit 13 sets the contents specified 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 unit 13 includes a selection unit 131 and a reading unit 132.

When the requester 15 notifies that "there is a transmit descriptor to be executed (read)", the selection unit 131 refers to the descriptor memory 14 corresponding to the requester 15 and transmits the descriptor memory 14. Get the descriptor. For example, when the selection unit 131 is notified by the first requester 15 (0) that "there is a transmission descriptor to be read", the selection unit 131 stores it in the first descriptor memory 14 (0) corresponding to the first requester 15 (0). Get the transmit descriptor that has been created. Similarly, when the selection unit 131 is notified by the nth requester 15 (n-1) that "there is a transmission descriptor to be read", the nth descriptor memory 14 corresponding to the nth requester 15 (n-1) Acquire the transmission descriptor stored in (n-1).

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

When the selection unit 131 is notified by each of the plurality of requesters 15 that "there is a transmission descriptor to be read" at substantially the same time, the selection unit 131 determines the order of the transmission descriptors to be read (executed), that is, 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 by each of the plurality of requesters 15 that "there is a transmission descriptor to be read" at substantially the same time, 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 of which is 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 the priority P" of each of the plurality of transmission descriptors, that is, of the plurality of transmission descriptors. Determine the execution order. Specifically, the selection unit 131 preferentially (that is, earlier) from among the plurality of transmission descriptors based on "at least one of the transmission time TT and the 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 by each of the first requester 15 (0) and the second requester 15 (1) that "there is a transmission descriptor to be read" at substantially the same time, the selection unit 131 executes the following processing. .. That is, the selection unit 131 refers to the first descriptor memory 14 (0) corresponding to the first requester 15 (0), and refers to the transmission descriptor (for example, the descriptor A) stored in the first descriptor memory 14 (0). ) Is obtained. Similarly, the selection unit 131 refers to the second descriptor memory 14 (1) corresponding to the second requester 15 (1), and refers to the transmission descriptor (for example, the descriptor) stored in the second descriptor memory 14 (1). B) is acquired.

The selection unit 131 acquires "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 the descriptor A and the descriptor B based on "at least one of the transmission time TT and the priority P" of each of the descriptor A and the descriptor B.

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

When the selection unit 131 notifies the transmission descriptor, the reading unit 132 reads the notified transmission descriptor, that is, executes the transmission descriptor notified by 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 the transfer process according to the contents specified in the read transmission descriptor, that is, the DMAC 12 transfers the transmission data from the main memory 20 to the buffer 162 according to the read transmission descriptor. Transfer.

The transmit descriptor (descriptor data) is stored in the descriptor memory 14 in a FIFO (first in, first out, first in, first out) method. When the CPU 30 completes the setting (storage) of the 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 unit 13 (particularly, the selection unit 131) that "there is a transmit 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 (particularly, the selection unit 131) that "there is no transmit descriptor to be executed", or "executes". Do not notify that there is a transmit descriptor to be sent.

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

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

The requester 15 further includes a setting register 151. The "execution number" and "execution number" notified from the CPU 30 to the communication controller 10 are stored in the setting register 151. Details of the "number of executions" and the "execution number" will be described later.

The BUF management unit 16 controls the transmission order of the transmission data and the actual transmission time RTT, 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 unit 16 includes a time designation transmission management unit 161 and a buffer 162.

The time-designated 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 the data (transmission data) is stored in the buffer 162, the time designation transmission management unit 161 confirms the transmission time TT specified by the transmission descriptor corresponding to the transmission data. Then, the time-designated transmission management unit 161 outputs a transmission request to the arbitration unit 17 when the transmission time TT confirmed by the current time CT is reached. The time-designated transmission management unit 161 transmits the transmission data to the network 3 as a response from the arbitration unit 17 that has received the transmission request, if there is an access permission.

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

The arbitration unit 17 adjusts a plurality of transmission requests to the network 3, that is, when the transmission times TT of the transmission data stored in each of the plurality of buffers 162 are substantially the same, any of the transmission data Decide whether time transmission should be prioritized.
In other words, when the arbitration unit 17 receives the transmission requests related to the transmission data stored in each of the plurality of buffers 162 at substantially the same time, the arbitration unit 17 selects the transmission request to which the access permission is given.

Here, the buffer 162 is roughly divided into a normal transmission buffer and a special transmission buffer, and when the transmission request related to the transmission data stored in each of the normal transmission buffer and the special transmission buffer is received substantially at the same time, the arbitration unit 17 receives. , Execute the following processing. That is, the arbitration unit 17 gives priority to the transmission request related to the transmission data stored in the special transmission buffer over the transmission request related to the transmission data stored in the normal transmission buffer. That is, the arbitration unit 17 grants access permission to the transmission request related to the transmission data stored in the special transmission buffer.

§3. Operation example (Overview of processing executed by the communication controller)
FIG. 3 is a flow chart illustrating an outline of processing executed by the communication controller 10.
As shown in FIG. 3, first, the descriptor execution management unit 13 (particularly, the selection unit 131) acquires at least one of the transmission time TT and the priority P defined in each of the plurality of descriptors (S10). .. Then, the selection unit 131 selects a descriptor to be read from the plurality of descriptors based on the acquired "at least one of the transmission time TT and the priority P of each of the plurality of descriptors" (S20). When the selection unit 131 selects a descriptor to be 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, and the like specified 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 processes executed by the communication controller 10 described with reference to FIG. 3 can be organized as follows. That is, the process (control method) executed by the communication controller 10 is a communication control device that transfers data (transmission data) from the main memory 20 to the buffer 162 according to the read transmission descriptor and transmits the transferred data to the buffer 162. It is a control method of.

The control method executed by the communication controller 10 includes a selection step (S20) and a read step (S30). The selection step is a process of selecting a descriptor to be read from a 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 a 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. Is. Further, the read 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 is selected 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. Then, the control method executed by the communication controller 10 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 control method executed by the communication controller 10 selects the descriptor to be read from the plurality of transmission descriptors one by one based on at least one of the transmission time TT and the 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 mounting 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 reading order of the plurality of transmission descriptors to output the processing result output by the software (processor). Control the order of data transmission. That is, the software can treat the communication controller 10 that executes the control method as one piece of hardware including a plurality of transmission queues that manage "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 of transmission data and actual transmission time RTT").

Therefore, the control method executed by the communication controller 10 has an effect that the processing load of the software can be reduced while suppressing the mounting size of the communication controller 10.

As described above, the communication controller 10 selects the descriptor to be read (that is, the descriptor to be executed) by using at least one of the transmission time TT and the priority P, that is, the read order (execution order) of the plurality of descriptors. To control. Therefore, the communication controller 10 reduces the processing load of 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 the transmission data", while suppressing the mounting size. be able to.

Here, the developer of the communication controller 10 further assumes the following cases 1, 2, and 3, and preferably selects a descriptor to be read even when the communication controller 10 faces these three cases. I devised so that I could select it. The details will be described below.

(In case 1, when the descriptor is selected only by priority)
FIG. 4 is a diagram illustrating a situation that occurs when a descriptor to be executed first (that is, to be read first) is selected based only on the priority P in the descriptor in Case 1. In case 1, the transmission time TT (low priority) specified by the descriptor set with the low priority P is earlier than the transmission time TT (high priority) specified by the descriptor set with the high priority P. , The time interval between the transmission times TT of both is large. In the following, a descriptor having a low priority P set may be referred to as a "low priority descriptor", and a descriptor having a high priority P 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, TX0, that is, the first descriptor memory 14 (0) is defined as “9:05” as the transmission time TT (0) of the transmission data D (0), and the transmission data D is defined. A descriptor in which "1" is specified 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 defined. The descriptor that defines "2" is stored.

That is, in case 1, the high priority descriptor is stored in TX0, and the 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 is specified by the low-priority descriptor stored in TX1. The “transmission time TT (1)” of the transmission data D (1) is “9:00”. The transmission time TT (1): "9:00" specified by the low priority descriptor is earlier than the transmission time TT (0): "9:05" specified by the high priority descriptor. 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 transmission times TT of both is large. That is, 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). ) Is large in time interval.

In case 1, when the descript to be executed first is selected only by the "priority P" specified by the descriptor, the high priority descriptor stored in TX0 precedes the low priority descriptor stored in TX1. Is executed.

By executing the high-priority descriptor before the low-priority descriptor, the data D (0) corresponding to the high-priority descriptor is buffered 162 (BUF) before the data D (1) corresponding to the low-priority descriptor. ) Is stored.

In the example shown in FIG. 4, after the data D (0) is stored in BUF0, that is, the first buffer 162 (0), the data D (1) is stored in BUF1, that is, the second buffer 162 (1). Has been done. It is not essential to separate the buffer 162 that stores the data D (0) and the buffer 162 that stores the data D (1), and both may be stored in the same buffer 162. For example, the data D (0) and the data D (1) may be stored in the same buffer 162 in the order in which the corresponding descriptors are executed (read). In FIG. 4, the data D (0) is stored in the BUF 0 so that it is easy to understand that the data D (0) is stored in the buffer 162 (BUF) before the data D (1). Only an example of storing D (1) in BUF1 is shown.

Since the data D (0) is stored in the buffer 162 before the data D (1), the data D (1) is transmitted to the network 3 and the data D (0) is transmitted to the network 3. Will be 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 data D (1) is transmitted to the network 3. Therefore, the transmission data D (1) cannot be transmitted to the network 3 at the transmission time TT (1) of "9:00".

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

In case 2 illustrated in FIG. 5, TX0 defines “9:01” as the “transmission time TT (0)” of the transmission data D (0), and “priority P” of the transmission data D (0). The descriptor that defines "1" is stored. Further, in TX1, "9:00" is specified as the "transmission time TT (1)" of the transmission data D (1), and "2" is specified as the "priority P" of the transmission data D (1). The descriptor is stored.

That is, in case 2, the high priority descriptor is stored in TX0, and the 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 is specified by the low-priority descriptor stored in TX1. The “transmission time TT (1)” of the transmission data D (1) is “9:00”. The transmission time TT (0): "9:00" specified by the low priority descriptor is earlier than the transmission time TT (1): "9:00" specified by the high priority descriptor. The time interval between the transmission time TT (1) of the transmission data D (1): "9:00" and the transmission time TT (0) of the transmission data D (0): "9:01" is "1". The time interval between the transmission time TT (1) and the transmission time TT (0) is small. That is, 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). ) Is small in time interval.

In case 2, when the descript to be executed is selected only by the "transmission time TT" specified by the descriptor, the low priority descriptor stored in TX1 is executed before the high priority descriptor stored in TX0. Will be done.

By executing the low-priority descriptor before the high-priority descriptor, the data D (1) corresponding to the low-priority descriptor is buffered 162 (BUF) before the data D (0) corresponding to the high-priority descriptor. ) Is stored.

In the example shown in FIG. 5, after the data D (1) is stored in BUF1, that is, the second buffer 162 (1), the data D (0) is stored in BUF0, that is, the first buffer 162 (0). Has been done. It is not essential to separate the buffer 162 that stores the data D (0) and the buffer 162 that stores the data D (1), and both may be stored in the same buffer 162. For example, the data D (0) and the data D (1) may be stored in the same buffer 162 in the order in which the corresponding descriptors are executed (read). In FIG. 5, the data D (0) is stored in the BUF 0 so that it is easy to understand that the data D (1) is stored in the buffer 162 (BUF) before the data D (0). Only an example of storing D (1) in BUF1 is shown.

Since the data D (1) is stored in the buffer 162 before the data D (0), the data D (1) is transmitted to the network 3 when the data D (0) is transmitted to the network 3. Will be executed later. That is, after the transmission data D (1) is transmitted to the network 3 at the transmission time TT (1): "9:00", the data D (0) is transmitted to the network 3. Therefore, the transmission data D (0) cannot be transmitted to the network 3 at the transmission time TT (0) of "9:01".

(Ingenuity assuming case 1 and case 2)
The developer of the communication controller 10 has further devised the communication controller 10 so that the descriptor to be read by the communication controller 10 can be appropriately selected in both cases 1 and 2 described above.

Specifically, the communication controller 10 executes the following processing 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 (high priority data) corresponding to the high priority descriptor and the transfer time RT of the data (low priority data) corresponding to the low priority descriptor 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". The “transfer time RT” is a time (period) required to transfer a certain data (a certain transmission data) from the main memory 20 to the buffer 162.

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

Here, when the scheduled total time ERT is larger (slower) than the transmission time TT (high priority), the communication controller 10 sends the high priority data to the buffer 162 even after transferring the low priority data to the buffer 162. The transfer can be made in time for the transmission time TT (high priority). That is, when the scheduled total time ERT is later than the transmission time TT (high priority), the communication controller 10 has high priority before the transmission time TT (high priority) even after transferring the low priority data to the buffer 162. Data can be transferred to buffer 162.

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

Further, when the scheduled total time ERT is smaller (earlier) than the transmission time TT (high priority), the communication controller 10 transmits the transfer of the high priority data to the buffer 162 after transferring the low priority data to the buffer 162. It is not possible to make it in time for the time TT (high priority). That is, when the scheduled total time ERT is earlier than the transmission time TT (high priority), the communication controller 10 buffers the high priority data after transferring the low priority data to the buffer 162 and before the transmission time TT (high priority). Cannot transfer to 162.

Therefore, when 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 chart showing an example of a selection process (a 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. Is. Specifically, FIG. 6 shows the process of "selecting which descriptor of the high-priority descriptor and the low-priority descriptor should be executed first (should be read first)" executed by the selection unit 131. It is a flow figure explaining the details.

As shown in FIG. 6, first, the selection unit 131 determines whether the transmission time TT (low priority) of the low priority descriptor is earlier than the transmission time TT (high priority) of the high priority descriptor (S110). ). When "the transmission time TT (high priority) is earlier than the transmission time TT (low priority), or both are the same" (NO in S110), the selection unit 131 includes the high priority descriptor and the low priority descriptor. Among them, the high priority descriptor is selected (S140).

When "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 described above, the scheduled total time ERT adds 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. Time.

Then, the selection unit 131 determines "whether the scheduled total time ERT is larger than the transmission time TT (high priority) specified in the high priority descriptor (the scheduled total time ERT is later)" (S130). When "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). ..

When "the scheduled total time ERT is earlier than the transmission time TT (high priority), or both are the same" (NO in S130), the selection unit 131 is the low priority descriptor of the high priority descriptor and the low priority descriptor. Is selected (S140).

(For Case 1 and Case 2, the selection result of the communication controller according to this embodiment)
FIG. 7 is a diagram illustrating a descriptor selected by the selection unit 131 by executing the flow illustrated in FIG. 6 by the selection unit 131.

As described above, in Case 1, in TX0, “9:05” is defined as the “transmission time TT (0)” of the transmission data D (0), and as the “priority P” of the transmission data D (0). A high-priority descriptor that defines "1" is stored. Further, in TX1, "9:00" is specified as the "transmission time TT (1)" of the transmission data D (1), and "2" is specified as the "priority P" of the transmission data D (1). Contains low priority descriptors.

Here, the transfer time RT (high priority) required for transferring the data corresponding to the high priority descriptor (high priority data) from the main memory 20 to the buffer 162 is “2”. The transfer time RT (low priority) required for transferring the data corresponding to the 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 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". ".

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 a low priority descriptor (a 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 described above, in Case 2, "9:01" is defined as the "transmission time TT (0)" of the transmission data D (0) in TX0, and is set as the "priority P" of the transmission data D (0). A high-priority descriptor that defines "1" is stored. Further, in TX1, "9:00" is specified as the "transmission time TT (1)" of the transmission data D (1), and "2" is specified as the "priority P" of the transmission data D (1). Contains low priority descriptors.

Here, the transfer time RT (high priority) required for transferring the data corresponding to the high priority descriptor (high priority data) from the main memory 20 to the buffer 162 is “2”. The transfer time RT (low priority) required for transferring the data corresponding to the 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 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". ".

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 a high-priority descriptor (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 the descriptor is selected in consideration of the priority and the transmission time)
FIG. 8 is a diagram showing a specific processing example when the flow illustrated in FIG. 6 is executed in case 1. As described above, when the high-priority descriptor is executed after the low-priority descriptor is executed, the time at which 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 set to "09". : 02 ". The scheduled total time ERT "09:02" is earlier than the transmission time TT (high priority): "9:05" specified in the high priority descriptor in Case 1.

Therefore, the selection unit 131 selects a low priority descriptor (a 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. ..

By executing the low-priority descriptor before the high-priority descriptor, the data D (1) corresponding to the low-priority descriptor is buffered 162 (BUF) before the data D (0) corresponding to the high-priority descriptor. ) Is stored.

Therefore, after the data D (1) stored earlier in the buffer 162 is transmitted, the data D (0) stored in the buffer 162 is transmitted after the data D (1). Specifically, the communication controller 10 (particularly, the time designation transmission management unit 161) converts the data D (1) previously stored in the buffer 162 into the “transmission time TT (1)” of the transmission data D (1). It is transmitted at "9:00". Then, the communication controller 10 (particularly, the time designation transmission management unit 161) transmits the data D (0) stored in the buffer 162 after the data D (1) after the data D (1) is transmitted. The data is transmitted at "9:05" which is the "transmission time TT (0)" of (0).

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

(In case 2, when the descriptor is selected in consideration of the priority and the transmission time)
FIG. 9 is a diagram showing a specific processing example when the flow illustrated in FIG. 6 is executed in case 2. As described above, when the high-priority descriptor is executed after the low-priority descriptor is executed, the time at which 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 set to "09". : 02 ". The scheduled total time ERT "09:02" is later than the transmission time TT (high priority): "9:01" specified in the high priority descriptor in Case 2.

Therefore, the selection unit 131 selects a high-priority descriptor (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. ..

By executing the high-priority descriptor before the low-priority descriptor, the data D (0) corresponding to the high-priority descriptor is buffered 162 (BUF) before the data D (1) corresponding to the low-priority descriptor. ) Is stored.

Therefore, after the data D (0) stored earlier in the buffer 162 is transmitted, the data D (1) stored in the buffer 162 is transmitted after the data D (0). Specifically, the communication controller 10 (particularly, the time designation transmission management unit 161) converts the data D (0) previously stored in the buffer 162 into the “transmission time TT (0)” of the transmission data D (0). It is transmitted at "9:01". Then, the communication controller 10 (particularly, the time designation transmission management unit 161) sets the data D (1) stored in the buffer 162 after the data D (0) at the earliest possible timing after the data D (0) is transmitted. 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 described so far with reference to FIGS. 4 to 9 can be organized as follows. That is, for the communication controller 10, when the priority P of a certain transmission descriptor among a plurality of transmission descriptors is higher than the priority P of another descriptor, the selection unit 131 executes the following processing. First, the selection unit 131 is the scheduled total time, which is "the time obtained by adding the data transfer time RT corresponding to the certain transmission descriptor and the data transfer time RT corresponding to the other descriptor to the current time CT". Calculate ERT. The transfer time RT is the time required to transfer the data (transmission data) from the main memory 20 to the buffer 162. Then, the selection unit 131 compares the calculated total scheduled time ERT with the transmission time TT of a certain transmission descriptor.

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

According to the above configuration, when the priority P of one transmission descriptor is higher than the priority P of another descriptor, the communication controller 10 determines the scheduled total time ERT and the transmission time TT of the certain transmission descriptor. To compare. Then, when the transmission time TT of the certain transmission descriptor is later than the scheduled total time ERT (later), the communication controller 10 selects the other descriptor in preference to the certain transmission descriptor. Further, if the transmission time TT of the certain transmission descriptor is before the scheduled total time ERT, the communication controller 10 selects the certain transmission descriptor in preference to the other descriptor.

Here, when a descriptor to be read is selected based only on the priority P specified in each of the plurality of transmission descriptors, the descriptor having the lower priority P is always read after the descriptor having the higher priority P. Will be (executed).

However, when the transmission time TT of another descriptor having a priority P lower than that of one transmission descriptor is sufficiently earlier than the transmission time TT of the certain transmission descriptor, the descriptor reading order is determined only according to the priority P. Is not always appropriate.

For example, even 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 mainly transmitted before the transmission time TT of the certain transmission descriptor. It may be possible to transfer to the memory 20. In such a case, the other descriptor should be read (executed) and then the certain descriptor should be read, that is, the other descriptor should be read before the certain transmit descriptor.

Further, when the descriptor to be read is selected based only on the transmission time TT specified in each of the plurality of descriptors, the descriptor having the late transmission time TT is always read after the descriptor having the early transmission time TT. become.

However, when the transmission time TT of another descriptor having a priority P lower than that of one descriptor is immediately before the transmission time TT of the certain descriptor, determining the descriptor read order according only to the transmission time TT may not be possible. Not always appropriate.

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

The communication controller 10 compensates for the above-mentioned deficiencies of each of the determination of the descriptor reading order according to the priority P only and the determination of the descriptor reading order according only to the transmission time TT. That is, when the priority P of a certain transmission descriptor among a 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. To compare. Then, the communication controller 10 selects the descriptor to be read, that is, the 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 an effect that the descriptor to be read can be appropriately selected as compared with the method of selecting the descriptor to be read according to only one of the priority P and the transmission time TT.

(Example of calculating transfer time)
FIG. 10 is a table in which information used by the communication controller 10 for calculating the transfer time RT of a certain transmission data is organized. Specifically, the communication controller 10 (particularly, the selection unit 131) has a data size of a certain transmission data and "a transfer rate when the communication controller 10 transfers data from the main memory 20 to the buffer 162". From, the transfer time RT of a 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 (particularly, the buffer 162) at the time of starting the PLC 1 (particularly at the time of establishing the protocol). Can be done. For example, when the main memory 20 and the communication controller 10 are connected by PCIe (Peripheral Component Interconnect Express), the communication controller 10 confirms the rate (theoretical value) guaranteed by the PCIe standard by referring to the register. ..

Here, each of the "execution rate" and the "overhead" is prepared in advance for each rate (theoretical value). Specifically, the "execution rate" is tuned for each rate (theoretical value) at the time of production (development) of the communication controller 10. The "execution rate" may be set by software (that is, CPU 30) at the time of starting PLC1. Similarly, the "overhead" is tuned for each rate (theoretical value) at the time of production (development) of the communication controller 10.

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

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

The communication controller 10 (particularly, the selection unit 131) uses the following equations from the transfer size of the acquired transmission data and the “transfer speed” and “overhead” for each rate (theoretical value) to transmit the transmission data. The transfer time RT of is calculated. That is, the communication controller 10 calculates the transfer time RT of the transmission data from "transfer time RT = {overhead + (transfer size / transfer speed)}".

(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 descriptor defines a time separated from the current time CT by a predetermined time or more as a "transmission time TT". In FIG. 11, the communication controller 10 is abbreviated as "NIC".

In case 3 illustrated in FIG. 11, TX0 defines “9:10” as the “transmission time TT (0)” of the transmission data D (0), and “priority P” of the transmission data D (0). The descriptor that defines "1" is stored. Further, in TX1, "9:00" is specified as the "transmission time TT (1)" of the transmission data D (1), and "1" is specified as the "priority P" of the transmission data D (1). The descriptor is 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 the transmission data D (2) “ A descriptor in which "2" is specified 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 the "low priority descriptor stored in TX2" is executed. Then, the situation shown in FIG. 11 occurs. It should be noted that, after executing the "high priority descriptor stored in TX0", the "low priority descriptor stored in TX2" is executed even if the "high priority descriptor stored in TX1" comes first. It may be 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. NS.

Then, 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 the high-priority data D (0) is stored before the high-priority data D (1) in the buffer 162, the high-priority data D (0) must be transmitted to the network 3 before the high-priority data D (0) is transmitted. Data D (1) cannot be transmitted to network 3.

Here, as described 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 "9:10". Therefore, the transmission data D (1) cannot be transmitted to the network 3 at "9:00", and the transmission data D (1) can be transmitted to the network 3 at the timing when the transmission data D (0) is "9:". After transmitting to network 3 in "10".

As shown in FIG. 11, in Case 3, a descriptor (eg, “Transmission time TT”) that defines a time (for example, transmission time TT (0)) separated from the current time CT by a predetermined time or more is defined as “transmission time TT” (eg, “Transmission time TT”). "High priority descriptor stored in TX0") has occurred. In case 3, further, after the descriptor defining the transmission time TT (0) as the “transmission time TT”, the “transmission time TT closer to the current time CT than the transmission time TT (0) (eg, the transmission time TT (1)) ) Is specified as "transmission time TT". "

In case 3, the "descriptor that defines the transmission time TT (0) as the" transmission time TT "" that occurred earlier is earlier than the "descriptor that defines the transmission time TT (1) as the" transmission time TT "". If this is executed, the situation shown in FIG. 11 will occur. That is, the data corresponding to the "descriptor that defines the transmission time TT (0) as the" transmission time TT "" becomes an obstacle, and the "descriptor that defines the transmission time TT (1) as the" transmission time TT "" The data corresponding to the above cannot be transmitted at the transmission time TT (1).

(Ingenuity assuming case 3)
The developer of the communication controller 10 has further devised the following device for the communication controller 10 so that the descriptor to be read by the communication controller 10 can be preferably selected even in the above case 3.

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

In the communication controller 10, the period obtained by subtracting the "current time CT" from the "transmission time TT specified by the descriptor" is larger than the determination time JT, that is, "(transmission time TT-current time CT)> determination time JT". If, then the descriptor is not executed. In the communication controller 10, when the period obtained by subtracting the "current time CT" from the "transmission time TT specified by the descriptor" is equal to or less than the determination time JT, that is, "(transmission time TT-current time CT) ≤ determination time JT". Then, the descriptor is executed.

FIG. 12 is a diagram showing a specific processing example realized by the communication controller 10 provided with the determination time JT for the case 3. As described above, in Case 3, in TX0, “9:10” is defined as the “transmission time TT (0)” of the transmission data D (0), and as the “priority P” of the transmission data D (0). The descriptor that defines "1" is stored. Further, in TX1, "9:00" is specified as the "transmission time TT (1)" of the transmission data D (1), and "1" is specified as the "priority P" of the transmission data D (1). The descriptor is stored. Further, in TX2, "9:00" is specified as the "transmission time TT (2)" of the transmission data D (2), and "2" is specified as the "priority P" of the transmission data D (2). The descriptor is stored.

The communication controller 10 sets the descriptor in which "9:10" is defined as the "transmission time TT (0)" of the transmission data D (0) until the descriptor reaches "the time retroactive from the determination time JT from" 9:10 "". , Do not run. That is, while "the time (period) obtained by subtracting the current time CT from the transmission time TT is larger than the determination time JT", the communication controller 10 does not read (do not execute) the descriptor that defines the transmission time TT.

Then, the communication controller 10 sets the descriptor in which "9:00" is defined as the "transmission time TT (1)" of the transmission data D (1), and the "period obtained by subtracting the current time CT from" 9:00 "". When the judgment time is JT or less, the data is executed. That is, when "the time obtained by subtracting the current time CT from the transmission time TT is equal to or less than the determination time JT", the communication controller 10 regards the descriptor defining the transmission time TT as the descriptor to be read, in other words, the selection unit 131. It is the target of the selection process by.

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 the TX1” in the buffer 162 before the high-priority data D (0).

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

The contents described so far with reference to FIGS. 11 and 12 can be organized as follows. That is, the determination time JT is set in advance in the communication controller 10, and the reading unit 132 reads the transmission descriptor after the determination time JT is set 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 is set back from the transmission time TT of the transmission descriptor.

Here, when another descriptor whose transmission time TT is closer to the current time CT than the transmission time TT of the certain transmission descriptor is generated after reading a certain transmission descriptor, the following problem occurs. .. That is, there arises a problem that the data corresponding to the certain transmission descriptor becomes an obstacle and the data corresponding to the other descriptor cannot be transmitted at the transmission time TT of the other descriptor.

This is because the data stored in the buffer 162 is transmitted in the order in which they are stored. That is, if the data corresponding to a certain transmit descriptor is stored before the data corresponding to another descriptor, the data corresponding to the certain transmit descriptor must be transmitted before the data corresponding to the other descriptor is transmitted. No data is sent. Then, the data corresponding to the certain transmission descriptor is not transmitted unless the transmission time TT of the certain transmission descriptor is reached. However, since the transmission time TT of the certain transmit descriptor is later than the transmission time TT of the other descriptor, the data corresponding to the other descriptor is transmitted at the transmission time TT of the other descriptor. Can't.

Therefore, the communication controller 10 suppresses the possibility that the above-mentioned problem occurs by reading the transmission descriptor after the determination time JT is set back from the transmission time TT of the transmission descriptor. That is, the communication controller 10 is described above so that the certain transmission descriptor is not read before reading another descriptor whose transmission time TT is closer to the current time CT than the transmission time TT of a certain transmission descriptor. Perform the adjustment. In other words, the communication controller 10 adjusts the read time (execution time) of the certain transmission descriptor, and specifically, after the time is set back from the transmission time TT of the certain transmission descriptor to the determination time JT. , Read (execute) that certain transmit descriptor.

Therefore, it is possible to prevent the communication controller 10 from reading a certain transmission descriptor before reading another descriptor whose transmission time TT is a time closer to the current time CT than the transmission time TT of a 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, in each of Case 1, Case 2, and Case 3, it has been described that the communication controller 10 can execute (read) a plurality of descriptors to be executed in a desired order and at a desired timing. The process 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 flow chart showing a processing example executed by the CPU 30 and the requester 15. In particular, FIG. 13A shows a processing example executed by the CPU 30, and FIG. 13B shows the processing example executed by the requester 15. An example of 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 the number of executions of the transmission descriptor.

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

Since the communication controller 10 executes the transmission process, the process to be executed by the CPU 30 ends in 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 or not 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 (particularly, the requester 15) executes the following processing. 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 according to the received transmission request, and stores the acquired descriptor in the descriptor memory 14. Specifically, the descriptor to be acquired 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 acquired from the main memory 20. Then, the communication controller 10 (particularly, the requester 15) stores the acquired 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 the first descriptor memory 14 (0) to the nth descriptor memory 14 (n−) in the descriptor memory 14. It is stored in each of 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 according to the transmission request in the first descriptor memory 14 (0), the communication controller 10 puts "in the request register of the first requester 15 (0) corresponding to the first descriptor memory 14 (0). 1 ”is stored. Further, when the communication controller 10 stores the descriptor B acquired according to the transmission request in the second descriptor memory 14 (1), the communication controller 10 puts "in the request register of the second requester 15 (1) corresponding to the second descriptor memory 14 (1)". 1 ”is stored.

The requester 15 in which "1" is stored in the request register outputs "request signal = 1" notifying that "there is a transmit descriptor to be executed (read)" to the descriptor execution management unit 13 (S320). .. Then, the requester 15 determines whether or not 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 the transfer completion notification is received from the descriptor execution management unit 13.

When there is a transfer completion notification from the descriptor execution management unit 13 (YES in S330), the requester 15 stores "0" in the request register and 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 flow diagram showing a processing example executed by the descriptor execution management unit 13 and the BUF management unit 16, and in particular, FIG. 14A shows a processing example executed by the descriptor execution management unit 13. , FIG. 14B 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)). Judgment (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 for selecting 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 contents specified in the read transmit descriptor (S430). The transfer request is a transfer instruction to the DMAC 12, and specifically, "acquires transmission data from the main memory 20 according to the contents specified in the read transmission descriptor, and transfers the acquired transmission data to the buffer 162. Instruct DMAC12 to "do".

The descriptor execution management unit 13 determines from the DMAC 12 whether or not there is a transfer completion report indicating that "the transfer processing of the transmission data corresponding to the transfer request has been completed by the DMAC 12" (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 there is a transfer completion report from the DMAC 12 (YES in S440), the descriptor execution management unit 13 issues a transfer completion notification to the requester 15 (S450). The "transfer completion notification" is information indicating that "the transfer processing of the transmission data from the main memory 20 to the buffer 162 has been completed according to the contents specified in the transmission descriptor".

As shown in FIG. 14B, first, the BUF management unit 16 determines whether or not 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 the transmission data exists in the buffer 162.

When there is transmission data in the buffer 162 (YES in S510), the time designation 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 designation transmission management unit 161 waits until the current time CT becomes the transmission time TT of the transmission data existing in the buffer 162. I will do it.

When the current time CT becomes the transmission time TT of the transmission data existing in the buffer 162 (YES in S520), the time designation transmission management unit 161 issues a transmission request to the arbitration unit 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 confirms "whether the transmission of other transmission data is being executed", and when it is confirmed that the transmission of other transmission data is not being executed, outputs the access permission to the time-designated transmission management unit 161. do. The arbitration unit 17 does not output the access permission to the time designation transmission management unit 161 when the transmission of other transmission data is being executed.

The time designation transmission management unit 161 determines whether or not there is an access permission from the arbitration unit 17 (S540). If there is no access permission from the arbitration unit 17 (NO in S540), the time designation transmission management unit 161 (BUF management unit 16) waits until the access permission from the arbitration unit 17 is obtained.

When the access permission from the arbitration unit 17 is granted (YES in S540), the time designation 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 chart showing an example of the selection process (S420) illustrated in FIG. 14A. As described above, the descriptor execution management unit 13 determines the execution order for one or more transmission descriptors to be executed (read), and for example, selects a transmission descriptor to be executed from a plurality of transmission descriptors to be executed. Select one by one (selection process). The details of this selection process executed by the descriptor execution management unit 13 will be described below with reference to FIGS. 15 to 17.

As shown in FIG. 15, the descriptor execution management unit 13 sets “0” in each of the three variables of the current transmission time CST, the current priority CPR, and the current transfer time CRT (S1100). Hereinafter, the current transmission time CST, the current priority CPR, and the 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 one or more descriptors, each of which corresponds to a transmission request, and transmits the target descriptor with priority P. Acquire the time TT and the like (S1200). The "one or more descriptors each corresponding to the transmission request" is the "descriptor for which the transmission request was made (YES in S310) in (B) of FIG. 13".

In the following description, 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" to correspond to the target descriptor. The "transfer time RT" of the transmitted data is abbreviated as "NRT". In addition, the transmission data corresponding to the target descriptor may be abbreviated as "target data". Similarly, the descriptor that defines the contents corresponding to the current transmission time CST, the current priority CPR, and the current transfer time CRT is abbreviated as "current descriptor", and the transmission data corresponding to the current descriptor is abbreviated as "current". I have something 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 equal to or less than 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 larger than the determination time JT (NO in S1300), the descriptor execution management unit 13 confirms "whether all the descriptors for which transmission requests have been determined have been determined". (S1600). When the time obtained by subtracting the current time CT from the transmission time NST of the target descriptor is equal to or less than the determination time JT (YES in S1300), the descriptor execution management unit 13 compares the current priority CPR with the priority NPR of the target descriptor. (S1400).

Here, the process of S1300 is described with reference to FIG. 12, "The communication controller 10 reads (executes) the descriptor after" the time when the determination time JT is traced back from the transmission time TT specified by the descriptor ". ”)”.

That is, in S1300, when 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 the certain descriptor in the current time CT. Exclude from the selection process. When the current time CT is earlier than "the time retroactive from 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 the certain descriptor in the current time CT. Do not read that particular descriptor.

In S1300, when 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 the certain descriptor in the current time CT. Target of processing. When the current time CT is after "the time retroactive from the determination time JT from the transmission time TT specified by a certain descriptor", the descriptor execution management unit 13 performs selection processing for the certain descriptor in the current time CT. Run.

The descriptor execution management unit 13 that compares 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 that the priority NPR of the target descriptor is (1) the same as the current priority CPR, (2) higher than the current priority CPR, and (3) the current priority CPR. Update processing is executed for each of the low cases. 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 in detail with reference to FIGS. 16 and 17.

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

If all the descriptors that have been requested to be transmitted have not been determined (NO in S1600), the descriptor execution management unit 13 selects one of the undetermined descriptors as the "target descriptor" from the descriptors that have been requested to be transmitted. do. Then, the descriptor execution management unit 13 acquires the priority NPR, the transmission time NST, and the like of the selected target descriptor (S1700). Then, the descriptor execution management unit 13 executes the processing after S1300.

That is, the descriptor execution management unit 13 confirms whether or not there is a descriptor in the descriptor for which the transmission request has not been executed from S1200 (or S1700) to S1500. If there is a descriptor that has not executed the processes from S1200 (or S1700) to S1500, the descriptor execution management unit 13 executes the processes from S1700 to S1500 for the descriptor.

Finally, the descriptor execution management unit 13 selects the descriptor corresponding to the current transmission time CST, the current priority CPR, and the 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. It is a flow chart which shows.

(Example of update processing when the priority of the target descriptor is the same as the current priority)
When 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. 16A. 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 each value of the current transmission time CST, the current priority CPR, and the current transfer time CRT. (S1512). Specifically, the descriptor execution management unit 13 updates the value of the current transmission time CST according to 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 according to the value of the priority NPR of the target descriptor. Further, 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, when the "current transmission time CST = 0", the descriptor execution management unit 13 transitions to the next process as "YES in S1511", 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)
When 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. 16B. 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 both 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 according to 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 according to the value of the priority NPR of the target descriptor. Further, 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, when "current transmission time CST = 0", the descriptor execution management unit 13 transitions to the next process as "YES in S1521", 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 transfers the target data after the current transfer is executed (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 the target descriptor".

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

When 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). When the transmission time NST of the target descriptor is the same as the scheduled total time ERT, or the transmission time NST of the target descriptor is larger (later) than the scheduled total time ERT (NO in S1524), the descriptor execution management unit 13 ends the update process. do.

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

Therefore, S1524 in FIG. 16B makes the same determination as in 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 chart showing 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 transfers the target data after the current transfer is executed, and the end time (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 the target descriptor".

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

When the current transmission time CST is the same as the scheduled total time ERT or the current transmission time CST is larger (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 of FIG. 6” and the current descriptor corresponds to the “high priority descriptor of 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 of FIG. 17 makes the same determination as S130 of 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. Modification 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 control system 0, one network 3 is connected to PLC1 without going through a network hub 2, and for example, PLC1 and one or more network devices are communicably connected to each other in a one-stroke format. You may.

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

10 Communication controller (communication control device)
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 read step TT transmission time (scheduled transmission time)

Claims (5)

A communication control device that transfers data from the 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 specified in each of the plurality of descriptors.
A communication control device including a reading unit that reads the descriptor selected by the selection unit. When the execution priority of one descriptor among the plurality of descriptors is higher than the execution priority of another descriptor, the selection unit determines.
(A) The transfer time required to transfer the data corresponding to the certain descriptor from the main memory to the transmission buffer at the current time, and the data corresponding to the other descriptor from the main memory to the transmission buffer. The scheduled total time, which is the time obtained by adding the transfer time required to transfer to, is compared with (B) the scheduled transmission time of the certain descriptor.
When the scheduled transmission time of the certain descriptor is later than the scheduled total time, the other descriptor is selected in preference to the certain descriptor.
The communication control device according to claim 1, wherein when the scheduled transmission time of the certain descriptor is before the scheduled total time, the certain descriptor is selected in preference to the other descriptor. Judgment time is set in advance
The communication control device according to claim 1 or 2, wherein the reading unit reads the descriptor after a time that goes back from the scheduled transmission time of the descriptor to the determination time. The transmission buffer is
A normal transmission buffer in which the data corresponding to the descriptor is stored in the order of the descriptor read by the reading unit, and
The reading unit reads the descriptor between the time when the selection unit selects the descriptor corresponding to the data stored in the normal transmission buffer and the time when the data stored in the normal transmission buffer is transmitted. However, from claim 1, the descriptor includes 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. The communication control device according to any one of 3. It is a control method of a communication control device that transfers data from the main memory to a transmission buffer according to a read descriptor and transmits the data transferred to the transmission buffer.
A selection step of selecting a descriptor to be read from among the plurality of descriptors based on at least one of the scheduled transmission time and the execution priority specified in each of the plurality of descriptors.
A control method including a read step for reading the descriptor selected in the selection step.

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