JPS63184431A - Data transmission system - Google Patents

Abstract

PURPOSE:To realize a data transmission system with a simple control and constant reply time by providing a line access controller sending a communication right provision instruction at a prescribed period in a network system using a bus form communication medium. CONSTITUTION:A controller 1 is connected to slave stations 2-6 being transmitters via a transmission line 10 being a bus type communication medium. The controller 1 generates a control signal being a transmission right provision instruction controlling the line access of the slave stations 2-6 at a prescribed period. On the other hand, the slave stations 2-6 acquire the communication right by the reception of the transmission right provision instruction addressed to each slave station to apply line access. Thus, the data transmission system with constant reply time is realized by a simple control.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a data transmission system for a network system in which a plurality of transmission devices are connected to a bus-type communication medium and mutually transmit data.

[Prior Art] A typical line access method in a network system using a bus-type communication medium is C3MA/
There are CD methods, token passing methods, etc.

[Problems to be Solved by the Invention] However, although the C3MA/CD method has simple line access control, it has the disadvantage that when the load is high, contention occurs frequently, efficiency deteriorates, and response time becomes extremely slow. There is.

Further, although the above-mentioned problems have been solved in the token passing method, tokens must be managed in all transmission devices, making control complicated.

Another method is the polling/selecting method, but even with this method, the control up to the actual data transmission is complicated, and at least one transmission device has two methods: polling and selecting. Complex control procedures had to be managed.

[Means for Solving the Problems] The present invention has been made for the purpose of solving the above-mentioned problems, and as one means for achieving the above-mentioned objects, the tree embodiment has the following configuration.

That is, a control device that sends a transmission right grant command to the system at a predetermined period for each transmission device connected to the system;
Each transmission device is provided with a receiving means for receiving a transmission right granting command addressed to the device from the control device, and an access means for acquiring the transmission right to the system after receiving the transmission right granting command by the receiving means and making line access possible. Be prepared.

[Operations] With the above configuration, a data transmission system with a constant response time that is not affected by changes in load due to increases or decreases in system transmission amount is realized with a simple configuration and control.

[Example 1] Hereinafter, an example according to the present invention will be described in detail with reference to the drawings.

FIG. 1 is a network system configuration diagram of a data transmission system according to an embodiment of the present invention, and in the figure, 1 is a transmission right grant command that controls line access of each slave station in the network system of the tree embodiment. A control device that generates a control signal, slave stations (A-E) 2 to 6 connected to a transmission line 10 which is a bus-type communication medium, and 10 which is a transmission line which is a communication medium. Each slave station ANE (2 to 6) has a unique address a ”-a e shown in parentheses in the figure.
is assigned.

The block configuration of the control device 1 is shown in FIG.

The control device 1 includes an address storage circuit 21 that stores the addresses of all slave stations connected to the network, and a transmission line 1 that stores data of the maximum length of a transmission frame determined by the network.
A timer circuit 22 that activates the address storage circuit 21 and the control signal generation circuit 23 every predetermined time period (T) that is longer than the transmission time for transmitting data to A control signal generation circuit 23 reads out the address value, generates a control signal frame for the slave station having the address value, and outputs it to the transmission circuit 24, and the control signal frame from the control signal generation circuit 23 is sent to the transmission path. It is composed of a transmitting circuit 24 that transmits data onto the 10.

Next, the block configuration of each slave station is shown in FIG.

In FIG. 3, numeral 31 is a control unit that controls the entire slave station of this embodiment by performing data transmission control as shown in FIG. 33 is an address holding unit that holds an address value unique to the slave station; 34 is a receiving circuit that checks the ID in the transmission frame received by the reception circuit 32 and determines the type of the transmission frame. The ID control circuit 35 for discrimination is an address comparison circuit that compares the destination address information included in the ID and the address held in the address holding section 33.

Further, 36 is a reception buffer that temporarily holds received data;
37 is a transmission buffer that temporarily holds transmission data, 38 is a transmission circuit that sends transmission data to the transmission path 1o, and 39 is an information processing device.

FIG. 4 shows the format of the control signal frame 100 used in this embodiment, and FIG. 5 shows the format of the data frame 150.

In the figure, the first field of each transmission frame is an IT) field indicating the type of this transmission frame, and the control signal ID10I for the control signal 100 and the IT field for the data frame 150.
In this example, data frame ID 151 is stored. Further, 102 is a destination address representing a slave station that should receive or receive the transmission frame. Further, 152 is a source address representing the source of the transmission frame, and 153 is a data storage field.

Next, the communication control of this embodiment having the above configuration will be explained below with reference to the flowcharts of FIGS. 6 and 7.

FIG. 6 is a control flowchart of the control device 1, and the seventh
The figure is a control flowchart of a slave station.

First, the control of the control device 1 will be explained with reference to FIG.

When the control device 1 is powered on, initialization processing such as resetting the timer circuit 22 is executed in step S1.

As a result, the timer circuit 22 starts counting time. Therefore, in step s2, a predetermined time (T) longer than the time set in the predetermined timer circuit 22, that is, the transmission time for transmitting data of the maximum length of the transmission frame determined by the network onto the transmission path 10, elapses. wait. When the predetermined time (T) has elapsed, the process proceeds to step s3, where the timer circuit 22 updates the read address value of the address storage circuit 21 by one. In the initial state, this becomes the corresponding read address value of the slave station address value of the first slave station (for example, slave station A2). As a result, the corresponding slave station address is read from the address storage circuit 21 and output to the control signal generation circuit 23.

In the following step S4, a start signal is output from the timer circuit 22 to the control signal generation circuit 23. Control signal generation circuit 23
Then, as shown in step S5, the slave station address outputted from the address storage circuit 21 is read by this activation signal, and the control signal 100 shown in FIG. 4 is generated. Then, in step S6, this control signal 100 is outputted to the transmission circuit 24 and sent out to the transmission line 10. And again step S
2, and waits for the timer circuit 22 to start up again after a predetermined period of time has elapsed. Then, a control signal for the second slave station (for example, slave station B3) is output. When the control signal 100 for all the slave stations connected to the network is outputted in this way, the control signal 100 for the first slave station is outputted again.

Next, communication control in the slave station will be explained with reference to the flowchart in FIG.

When the slave station is powered on, first, initial processing is executed in step S11, and then in step S12, the receiving circuit 32
has received a transmission frame from the transmission path 10, that is, I
It is checked whether the D discrimination circuit 34 has detected the ID of the transmission frame. If the transmission frame has not been received, the reception of the transmission frame is waited here. When the transmission frame is received, the process proceeds to step 313, where the address comparison circuit 35 compares the destination area address 10 that is sent following the ID section.
It is checked whether the address value stored in 2 and the address value held in the address holding unit 33 are equal (whether or not the transmission frame is addressed to the own station). Here, if the two address values are different, the transmission frame is addressed to another station, so the process returns to step S12 and waits for the next transmission frame to be received.

If the two address values match, the transmission frame is addressed to the own station, so the process proceeds to step S14, where the determination result of the ID discriminating circuit 34 for the received ID field is checked to determine whether or not this is the control signal IDl0I. If the ID part is the control signal ID10I, the received transmission frame is the control signal 100, so the process proceeds to step S15, which means that the transmission right to the transmission path 10 has been acquired, and there is a transmission request from the information processing device 39 or the like. Find out whether or not.

If there is no data to be transmitted, the process returns to step S12 to prepare for reception of the next transmission frame. If there is data to be transmitted here, step S15 to step S
16, a transmission frame to be transmitted is generated and stored in the transmission buffer 37, for example. This can be done, for example, by setting the data frame ID 151 in the ID area, setting the slave station address of the desired data transfer destination in the destination address 102, setting the local station address value held in the address holding unit 33 in the source address 152, and Data to be transferred is set in area 153.

These necessary data are sent to the information processing device 39 prior to transmission.
It is desirable to generate and store the information in the transmission buffer 37 in advance, and check the transmission immediately after the above-mentioned reception. When the generation of the transmission frame is completed, it is sent onto the transmission line 10 via the transmission circuit 38 in step S17. When the transmission of the transmission frame to be transmitted is completed, the process returns to step S12 to prepare for reception of the next transmission frame.

On the other hand, if it is determined in step S14 that the control signal 100 is not being received, the data frame 150 is being received, so the process proceeds to step S20, where the data 153 is received together with the subsequently sent source address 152, and the data 153 is received in the reception buffer 36.
Store in. When all the data frames have been received, the control unit 31 leaves the information processing device to that effect, and requests the information processing device to receive the data from the reception buffer 36.

Note that if a reception error or the like occurs here, the next time the own station acquires the transmission right, it will output a retransmission request for this data frame and have it retransmitted so that it can receive it normally.

FIG. 8 shows an example of the flow of the transmission format output to the transmission line 10 as described above. The horizontal axis of the figure shows the passage of time.

First, the control device 1 sends a control signal 100 whose destination address 102 is [a] to the transmission line 10, and the slave station A2 receives it (201). When slave station A2 has data to transmit at this time and receives a transmission request, it sends data transmission frame 1.
50, and set the desired slave station address to the destination address 10.
2 to the transmission path 10 (202). The corresponding slave station will receive this data transmission frame.

Then, after (T) time has elapsed (wait for the maximum length of transmission time determined by the network), the control device 1 sends out the control signal 100 whose destination address 102 is [b] as the next control signal 100 (2 .03). When the slave station B3 which received this request does not have a transmission request, the slave station B3 does not transmit any transmission frame. Therefore, during this time, the transmission line 10
becomes a non-transmission state (204).

After the elapse of (T) time, the control device 1 sends the control signal 100 of [C] whose destination address 102 is the next address value to the transmission path 205), and the slave station C4 that received this control signal 100 transmits If there is a request, a data transmission frame to be transmitted is sent to the transmission path 10 (206).

As described above, by providing a line access generation device, each station can transmit data without causing collisions using a simple control method.

[Effects of the Invention] As explained above, according to the present invention, data transmission with a constant response time that is not affected by changes in load caused by increases or decreases in system transmission amount with simple configuration and control can be achieved. method can be realized.

[Brief explanation of the drawing]

Fig. 1 is a network system configuration diagram of an embodiment according to the present invention, Fig. 2 is a block diagram of a control device of this embodiment, Fig. 3 is a block diagram of a slave station of this embodiment, and Fig. 4 is a block diagram of a control device of this embodiment. FIG. 5 is a format diagram of a data transmission frame used in this embodiment. FIG. 6 is a control flowchart of the control device of this embodiment. FIG. 7 is a slave station of this embodiment. FIG. 8 is a diagram showing the state of sending a transmission frame to the transmission path in this embodiment. In the figure, 1...control device, 2-6...slave station, 10...
- Transmission path, 21... Address storage circuit, 22... Timer circuit, 23... Generation circuit, 24.38... Transmission circuit, 31... Control unit, 32... Receiving circuit, 33・
...Address holding unit, 34...ID discrimination circuit, 35.
...Address comparison circuit, 36...Reception buffer, 37
. . . transmission buffer, 39 . . . information processing device. Patent applicant Canon Co., Ltd. Figure 6 Figure 7

Claims (2)

[Claims] (1) In a data transmission method for a network system in which multiple transmission devices are connected to a bus-type communication medium and mutually transmit data, a command to grant transmission rights is issued at a predetermined period to each transmission device connected to the communication medium in the system. 1. A data transmission system comprising a line access control device for transmitting data, and each transmission device acquires communication rights by receiving a transmission right grant command addressed to itself and accesses a communication medium. (2) The data transmission system according to claim 1, wherein the sending cycle of the transmission right grant command is longer than the maximum sending time of transmission data per unit of the system.