JPH07115423A - Transmission control method - Google Patents

Abstract

PURPOSE:To continuously perform the operation without interrupting the business even in the case of the occurrence of a fault in one controller by providing plural controllers at the time of controlling many terminal equipment by the multi-drop system. CONSTITUTION:Controllers 11 and 12 which control plural terminal equipmentS 21 to 2n are provided. Controllers 11 and 12 alternately perform the polling and the processing of data from terminal equipmentS responding to this polling. Controllers monitor each other; and if the polling is not issued from one controller, the occurrence of a fault is discriminated, and the other controller performs the transmission control processing of all terminal equipments.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a transmission control system in which a plurality of terminals and the like are connected by a multi-drop system, and more particularly to a transmission control system capable of continuous operation while avoiding system down.

[0002]

2. Description of the Related Art FIG. 9 shows a configuration of a conventional transmission control system in which a plurality of terminals are connected by a multi-drop system. FIG. 10 shows a transmission control procedure in the configuration of FIG.

In FIG. 9, 1 is a pair of transmission lines, both ends of which are terminated by terminating resistors 2. Reference numeral 11 is a control device for controlling the terminals 21, 22 ,. The control device 11 is connected to the transmission line 1 via the driver 11D and the receiver 11R. Similarly, the terminals 21 to 2n are connected to the transmission line 1 via the drivers 21D to 2nD and the receivers 21R to 2nR. It should be noted that both the control device and the terminal require a microcomputer or a program for controlling the driver and the receiver, but they are omitted here.

In the configuration of FIG. 9, data transfer control is performed using the transmission control procedure shown in FIG. Since one control device and a plurality of terminals are connected to one transmission line, multi-drop control is performed. FIG. 10 shows a polling method.

That is, when the control device 11 issues p, which is polling for the address number 1, the terminal device corresponding to the address number responds with the data D, and responds nothing except the corresponding terminal device. Also, if there is no response data from the terminal, only a termination code is responded like EOT.

By sequentially issuing the above-mentioned polling to all terminals, data transfer control is performed. Note that, in FIG. 10, ACK, NAK, EOT, etc., which are commonly used when transmission control is performed, are omitted and only main parts are shown. Further, as one related to this type of transmission control system, for example, "EIA Standard RS-
There is 485 ".

[0007]

Since the above-mentioned conventional technique does not pay particular attention to the backup method when the control device becomes inoperable due to a failure or the like, the control device becomes inoperable due to the failure or the like. There was a problem that the system went down.

An object of the present invention is to provide a plurality of control devices when controlling a large number of terminals by the multi-drop method, and to enable continuous operation without interruption even if one control device fails. Another object of the present invention is to provide a transmission control method for a simple down system.

[0009]

In order to achieve the above object, in the invention according to claim 1, a plurality of terminals are connected to one line by a multi-drop method and at least two terminals are controlled. In a transmission control method in which two control devices are connected, during normal operation of each control device, the first and second control devices alternately issue polling, and process response data from the terminal to the polling, When one of the control devices fails, the normal control device substitutes the processing of the failed control device.

According to a second aspect of the invention, the start command for starting the second control unit after the first control unit issues polling and finishes data processing from the terminal for the polling. Is issued and the timer monitoring is started, and when the second control device does not issue polling even after a predetermined time has elapsed, it is determined that the second control device has failed.

According to another aspect of the present invention, the first control device issues a poll and the first
When there is a data processing request from the terminal, before issuing the data processing, after issuing a start command to the second control device and passing the line to the second control device,
When the data processing is started, the second control device issues a polling, and there is a data processing request from the second terminal for the polling, or there is no data processing request from the terminal, When the polling has reached the terminal immediately before the first terminal, the second control device issues a start command, returns the line to the first control device, and the first control device , Issues a selection for the first terminal, transfers the result of the data processing to the first terminal, and sends the selection result to the first terminal after the second terminal or to the first terminal. It is characterized by starting polling.

[0012]

By using a plurality of control devices, each control device alternately performs polling and data processing from the terminal for the polling. Each control unit monitors each other, and when the control unit does not issue polling, considers that control unit as a failure and logically disconnects it, and the remaining control units act on behalf of the failed control unit for transmission control. Perform processing.
As a result, the terminal can be continuously used without interrupting its operation, thus improving the operation rate.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be specifically described below with reference to the drawings. FIG. 1 shows the configuration of the transmission control system of the present invention. In the figure, 11 and 12 are two control devices provided by this embodiment. Reference numeral 1 is a pair of transmission lines, and 21 to 2n are n terminals. As described above, in this embodiment, a plurality of control devices (two in this example) are provided for controlling the plurality of terminals.

FIG. 2 shows the main structure of the interface section shown in FIG. Both ends of one pair of transmission lines 1 have a terminating resistor 2
Respectively terminated by. The control devices 11 and 12 are connected to the transmission line 1 via their drivers 11D and 12D and receivers 11R and 12R. In addition, the terminal group (21
2n) is similarly connected to the transmission line 1 via the drivers 21D to 2nD and the receivers 21R to 2nR. It should be noted that both the control device and the terminal require a micro computer or a program for controlling the driver and the receiver, but they are omitted here.

FIG. 3 shows an embodiment of a transmission control procedure by two control devices (Ha, Hb). That is, when the control device Ha issues the polling p for the address number 1, the terminal device corresponding to the address number responds the data of D and the other terminals do not respond. At this time, the control device Hb monitors whether or not the data transfer of the control device Ha is normally performed, and if the data transfer is normally completed, the control device Hb issues the polling p for the address number 2 and The response data D from the terminal corresponding to the address number is processed. At this time, the control device Ha monitors the control device Hb,
After confirming the end of the data transfer, the control unit Ha issues the next polling. Thereafter, the control devices Ha and Hb alternately issue polling and process response data to the polling.

FIG. 4 shows an embodiment of the operation when the controller Hb fails and polling cannot be issued in the above operating state, that is, an example of a transmission control procedure at the time of an abnormality. The control unit Ha issues the polling p and processes the response data D to it. Then, the control device Hb
Should issue the polling p, but cannot issue it due to a failure. In such a case, the control device Ha
After the completion of the response data D processing, the timer monitoring is started, and even if a certain period (here, Tout) has elapsed, the control device H
When the polling is not issued from b, it is considered that a failure has occurred, the control device Hb is logically separated, and the control device Ha performs the subsequent control.

FIG. 5 is an operation flowchart of the control unit Ha. First, a register X (not shown) in the control device is initialized to 1 (step 101). Issuing polling for the address number (X) (step 10)
2). In response to the polling, data is received from the terminal and it is checked whether the processing is completed (step 103). It monitors until it is completed, and when it is completed, it moves to the monitoring of the control device Hb as the next step.

First, a timer is set (step 1
04). Then, the time-out is monitored (step 10
5) If it has not timed out, it is checked whether the control device Hb has issued polling (step 106). Step 1 if no polling is issued
It monitors by the loop of 05 and 106. If polling is issued, move to data monitoring. First, the timer is set (step 107), the timeout is monitored (step 108) and the termination of the control device Hb is monitored (step 109), as described above.

If the control unit Hb is terminated normally, 2 is added to the register X (step 110). This indicates that the control devices Ha and Hb alternately perform polling. Next, it is determined whether or not the register X has become larger than n, which is the number of terminals (step 111), and if not larger, the process jumps to step 102, and if it becomes larger, the register X is initialized to 1 (step 112), and step Jump to 102. As a result, continuous polling can be repeated.

On the other hand, if the time-out occurs in steps 105 and 108, it means that polling cannot be issued due to a failure of the control device Hb. First, the control device Hb is logically disconnected from the line (step 201), and 1 is added to the register X (step 2).
02). Then, for the terminal with the address number (X),
A poll is issued (step 203) and its termination is monitored (step 204). If it is finished, it is judged whether or not the register X has become larger than n, which is the number of terminals (step 205). If it is not large, the routine jumps to step 202, and if it becomes large, the register X is initialized to 0 (step 206). ), Jump to step 202. That is, the control device Ha issues polling to all the terminals and substitutes the function of the control device Hb.

As described above, according to this embodiment, even if one of the control devices fails, the other control device can automatically perform control without interrupting the processing. Can be improved.

FIG. 6 shows the transmission control procedure of the second embodiment of the present invention. In the second embodiment, each control device is
As in the first embodiment (FIGS. 3 and 4), the data transfer of the other party is not monitored, but a kind of control code [a], [b] for instructing the other party to issue polling is issued, and transmission of the transmission is performed. The procedure for transferring the control right to the other control device is adopted.

That is, the controller Ha polls p
Is issued and the response data D corresponding thereto is processed, and a control code [b] for instructing the controller Hb to issue polling is issued. The control device Hb receiving the control code [b] issues the polling p, processes the response data D to the polling p, and controls the control device Hb.
A control code [a] for instructing a to issue polling is issued to a. Thereafter, similarly, the transmission control right is passed to the control device of the other party to perform data transfer.

FIG. 7 shows a transmission control procedure when the controller Hb fails in the transmission control procedure of the second embodiment. As described above, the controller Ha polls the polling p.
Is issued and the response data D corresponding thereto is processed, and a control code [b] for instructing the controller Hb to issue polling is issued.

The control device Hb receiving this control code [b]
Must issue poll p, but cannot issue poll due to a failure. In this case,
After issuing the control code [b], the control device Ha enters timer monitoring, and if polling is not issued from the control device Hb even after a certain period (here, Tout) has elapsed, it is considered that a failure has occurred, and control is performed. The device is logically separated, and the control device Ha performs the subsequent control.

As described above, according to the second embodiment, each control device only needs to monitor the timer until the control is handed to itself, and therefore the interface processing becomes very simple.

FIG. 8 shows the transmission control procedure of the third embodiment of the present invention. The third embodiment is more effective when a response is transferred from the control device to response data such as various inquiries, and when the control device takes a long processing time. It is a procedure.

That is, in FIG. 8, the control unit Ha
When receiving the response data D, first, the control code [b] is issued and the line is passed to the control device Hb.
The processing of the response data D is started. The control device Hb issues the polling p, but if the terminal device having the address number has no response data, it responds with EOT, which is a kind of termination control code. In this case, the control device Hb
Without passing the control right of the line to the control unit Ha, the next polling p is issued as it is. In the same manner, the control right of the line is maintained until the response data is generated in the same manner or until the polling of the terminal immediately before the control device Ha is processing the polling cycle is completed (it becomes p here). To do.

In the example of FIG. 8, the response data (15) D is generated in the polling (15) p, and the control device Hb issues the control code [a] to give the control right of the line to the control device Ha.
And the process of response data (15) D is started.

On the other hand, the control unit Ha issues the selection s for the address number 5 in order to transfer the processing result of the data D. The terminal receives the response data of A, which is the processing result for the data D, by responding to the selection with ACK, which is a kind of control code indicating that data reception is possible.
Then, the end control code EOT is transmitted, and the process ends.

The control unit Ha subsequently starts polling, but since the previous process by the control unit Hb has performed up to the address number 15, it starts from polling (16) p. In the above procedure, when there is no response data to the polling, the polling is performed once, but when the processing time in the control device is short, the number of polling may be set to a fixed number.

As described above, according to the third embodiment, the data processing can be performed by another control device during the repeated polling time period when there is no response data to the polling, so that the processing speed is improved. In addition, the load can be distributed.

[0033]

As described above, according to the first aspect of the invention, a plurality of control devices for controlling a plurality of terminals are provided, and when one control device fails, the other control device is provided. Since this process is performed on behalf of the system, continuous operation is possible without stopping the system, and a no-down system can be constructed.

According to the second aspect of the present invention, since one control device only monitors the timer after passing the transmission control right to the other control device, the interface processing becomes simple.

According to the third aspect of the present invention, since a plurality of control devices are simultaneously operated in the normal state, it is possible to distribute the load, improve the processing speed, and shorten the turnaround time. it can.

[Brief description of drawings]

FIG. 1 shows a configuration of a transmission control system of the present invention.

FIG. 2 shows a main configuration of an interface unit shown in FIG.

FIG. 3 shows a transmission control procedure of the first embodiment of the present invention.

FIG. 4 shows an example of a transmission control procedure when a control device fails in the transmission control procedure of the first embodiment.

FIG. 5 is an operation flowchart of the control device Ha.

FIG. 6 shows a transmission control procedure of the second embodiment of the present invention.

FIG. 7 shows a transmission control procedure when a control device fails in the transmission control procedure of the second embodiment.

FIG. 8 shows a transmission control procedure of a third embodiment of the present invention.

FIG. 9 shows a configuration of a conventional transmission control method.

FIG. 10 shows a conventional transmission control procedure.

[Explanation of symbols]

 1 Transmission Line 11, 12 Control Device 21-2n Terminal

Claims (3)

[Claims] 1. In a transmission control system in which a plurality of terminals are connected to one line by a multi-drop method and at least two control devices for controlling the terminals are connected, when each of the control devices operates normally. , The first and second control devices alternately issue polling, process response data from the terminal to the polling, and when one of the control devices fails, the normal control device determines that the failed control device Transmission control method characterized by performing the processing of 2. The first control device issues a polling command, terminates data processing from the terminal for the polling process, and then issues a start command for activating the second control device and a timer. Start monitoring, the second
2. The transmission control method according to claim 1, wherein the second control device is determined to be out of order when the control device does not issue polling even after a lapse of a predetermined time. 3. When the first control device issues a polling and there is a data processing request from the first terminal for the polling, the second control is performed before the data processing is performed.
Issue a start command to the second control device, pass the line to the second control device, then start the data processing, the second control device issues a polling, and responds to the polling. The second control is performed when there is a data processing request from the second terminal or when there is no data processing request from the terminal and the terminal immediately before the first terminal completes the polling cycle. The device issues a start command, returns the line to the first control device, the first control device issues a selection for the first terminal, and sends the selection of the data processing to the first terminal. The transmission control method according to claim 2, wherein the result is transferred, and polling is started for the next terminal of the second terminal or the first terminal.