JPH07212431A - Data transmission method of process control device - Google Patents

Abstract

(57) [Summary] [Object] In the process control device 1a, while performing normal control on the control target device 8, between the transmission device 7a and the transmission target device 9 connected via the modems 12a and 12b. Perform data transmission efficiently. [Configuration] The transmission device 7a sends out a control signal indicating its own operating state, which is transmitted to the transmission target device 9 via the modems 12a and 12b, based on a control command received from the process control device 1a. The process control device 1a also sends the above-mentioned control commands to the transmission device 7a in accordance with the control status of the controlled device 8. In addition, the process control device 1a according to another invention includes a modem 12a.
The control signal state of 12b is grasped, and each control command is sent to the transmission device 7a according to the grasped control signal state and the control situation for the controlled device 8.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a data transmission system of a process control device for controlling the operation of controlled equipment and transmitting data with the equipment to be transmitted.

[0002]

2. Description of the Related Art A process control device for controlling various equipment incorporated in a plant takes in process data indicating the operating state of each control device, executes a predetermined control operation, and controls the operation result as operation data. By sending to the target device, the operating state of the control target device is controlled to the target value.

Further, depending on the process control device, the process data fetched from the controlled device may be sent to the monitoring device via the transmission path and displayed on the CRT display screen of the monitoring device on the monitor. Further, the process control device sends the process data to the host system connected via the transmission path and controls the control target device according to the data received from the host system.

A process control system in which a process control device for controlling the control target device and transmitting data to the transmission target device such as a monitoring device and a host system as necessary is incorporated in FIG. It is configured as shown.

In the process control system of FIG. 4, the process control device 1 includes a CPU (central processing unit) 2,
2. Program memory (APM) for storing application programs Data memory (D
M) 4. Then, the input / output device 6 and the transmission device 7 are connected to the process control device 1 via the system bus 5.
And are connected.

A control target device 8 such as a production facility forming a plant is connected to the input / output device 6 via a signal cable 10. Further, a modem 12a is connected to the transmission device 7 via a transmission signal cable 11a that satisfies the RS232C standard. The other modem 12b is connected to the modem 12a via a modem-dedicated signal cable 13, and the above-mentioned transmission target device 9 is connected to this modem 12b via a transmission signal cable 11b.

FIG. 5 is a block diagram showing a main part of the transmission device 7 and a function related to data transmission of the process control device 1. In the program memory 3 of the process control device 1, in addition to a control program for controlling the control target device 8, a transmission task 30 for performing data communication with the transmission target device 9 via the transmission device 7 is stored. And again
In the data memory 4, a transmission data memory 40 that stores various data to be sent to the transmission target device 9 is formed. In addition, the transmission control device 7 includes a transmission control unit 70.
A transmission interface unit 71 and a transmission data memory 73
It consists of and.

Then, in the process control device 1, when the transmission task 30 is activated in response to the data transmission request,
The transmission task 30 sends a data transmission request to the transmission control unit 7
At the same time, the data stored in the transmission data memory 40 is read out and written into the transmission data memory 72 of the transmission device 7.

The transmission control unit 70 which has received the data transmission request
Reads out the data in the transmission data memory 72 and sends it to the modem 12a on the self side via the transmission interface unit 71 and the transmission signal cable 11a. The modem 12a is a signal cable 13. The data is transmitted to the transmission target device 9 via the modem 12b and the transmission signal cable 11b.

Further, in the process control device 1, when the transmission task 30 is activated by the generation of a data reception request, the transmission task 30 sends a data reception command to the transmission control unit 70. The transmission control unit 70 that has received the data reception command receives data from the transmission target device 9 via the modems 12b and 12a and the transmission interface unit 71. Transmission control unit 70
Stores the received data in the transmission data memory 72 and notifies the transmission task 30 of the process control device 1 of the reception completion.

Upon receiving the reception completion, the transmission task 30 transfers the data in the transmission data memory 72 to the transmission data memory 4
Transfer to 0. In this way, data is transmitted / received to / from the transmission target device 9.

Next, a procedure (communication protocol) for transmitting and receiving a control signal between the transmission device 7 and the transmission target device 9 using the modems 12a and 12b according to the RS232C standard will be described with reference to FIG.

The transmission device 7 and the transmission target device 9 are, as shown in the figure, a terminal 1 for transmitting a transmission data signal SD.
4a and 14b, terminals 15a and 15b for receiving the reception data signal RD, terminals 16a and 16b for transmitting the transmission request signal RS, terminals 17a and 17b for receiving the transmission permission signal CS, and a data set ready signal. Terminals 18a and 18b for receiving the DR, terminals 19a and 19b for transmitting the terminal device ready signal ER, and terminals 20a and 20b for receiving the carrier detection signal CD.
Is provided.

First, when the power supply of the entire process monitoring system is turned on and the system shifts to the initialization state, (1) the transmission device 7 turns on the terminal device ready signal ER of the modem control signal of the terminal 19a. When the terminal device ready signal ER of the terminal 19a is turned on, the modems 12a, 12b
The data set ready signal DR of the terminal 18b of the transmission target device 9 is turned on via. Therefore, the transmission target device 9 knows that the transmission device 7 is in the transmission possible state.

(2) When the device 9 to be transmitted is in a state capable of transmitting, the device ready signal ER of its terminal 19b is transmitted.
Turn on. Then, the data set ready signal DR of the terminal 18a of the transmission device 7 is turned on via the modems 12b and 12a. Therefore, the transmission device 7 is the transmission target device 1
9 knows that it has transitioned to the transmittable state.

(3) Further, the transmission device 7 and the transmission target device 9 have their own modems 12 because the carrier detection signals CD of the terminals 20a, 20b on their own side have changed to the ON state.
Understand that a and 12b are normal.

(4) When the above preparation process is completed and data is transmitted from the transmission device 7 to the transmission target device 9, the transmission device 7 turns on the transmission request signal RS of the terminal 16a.
Then, if the modem 12a can transmit data, the transmission permission signal CS to the terminal 17a of the transmission device 7 is turned on.
Then, the transmission device 7 can confirm that the data can be transmitted, and can transmit the data.

(5) Then, the transmission device 7 sends out the actual transmission data signal SD from the terminal 14a. The transmission target device 9 receives the data from the transmission target device 9 from the terminal 15b.

In this way, the transmission device 7 transmits and receives the above-mentioned control signals to transmit and receive data between the transmission task 30 and the transmission target device 9 in the process device 1.

[0020]

However, even in the data transmission system of the process control device in which the data transmission between the process control device 1 and the transmission target device 9 is performed by the above-mentioned procedure of transmitting and receiving each control signal. However, there were still the following issues to be improved.

The transmission and reception of each control signal described above is executed between the transmission device 7 and the transmission target device 9. The transfer of each control signal is executed asynchronously, completely independently of the control processing operation for the controlled device 8 in the process monitoring device 1.

Therefore, there are cases where the data transmission enabled state in the transmission device 7 and the control processing operation for the controlled device 8 of the process control device 1 do not coincide in timing. For example, when the transmission task 30 in the control processing operation of the process control apparatus 1 is still preparing for transmission control even if the transmission apparatus 7 can transmit data, data is frequently transmitted from the transmission target device 9 or the control processing operation is performed. Although only the data reception is prohibited, the transmission target device 9 often executes wasteful data transmission such as stopping the control processing operation of the process control device 1 and continuing the data transmission, and the transmission efficiency of the transmission path is improved. The problem of diminishing occurs.

In order to reduce such wasteful data transmission, the transmission target device 9 monitors the state of the control processing operation in the process control apparatus 1 by some means, and according to the state of the control processing operation. However, there is a problem in that the configuration of the entire system is complicated and the control processing operation and the transmission specification with the transmission target device 9 are limited.

Further, the transmission task 30 on the side of the process control device 1 has only means for recognizing the transmission stop on the side of the transmission target device 9 by the abnormality notification from the transmission device 7 after the data transmission request.

The present invention has been made in view of the above circumstances, and the process control device controls each control signal sent from the transmission device to the transmission target device.
While maintaining the control signal transmission / reception procedure of the conventional standard, wasteful data transmission / reception between the transmission device and the transmission target device can be reduced as much as possible to improve the data transmission efficiency, and the process control device and the transmission target device can process the data. It is an object of the present invention to provide a data transmission system of a process control device which is improved in efficiency and is easy to use.

[0026]

SUMMARY OF THE INVENTION In order to solve the above problems, the present invention provides transmission by interposing a transmission device and a modem between a process control device for controlling the operation of a control target device and a transmission target device. When receiving the data communication command from the process control device, the device performs data communication with the transmission target via the modem in accordance with a procedure for transmitting and receiving a predetermined control signal. A control signal, which is transmitted to the transmission target device via the modem and indicates the operating state of itself, is transmitted based on a control command received from the process control device. Further, the process control device sends a control command to the transmission device according to the control status of the control target device.

[0027] In still another invention, in the data transmission method described above, the process control device grasps the control signal state of the modem via the transmission device, and the grasped control signal state and the control situation for the controlled device are displayed. In response, a control command is sent to the transmission device.

[0028]

In the data transmission method of the process control device configured as described above, since the transmission device performs data communication with the transmission target device via the modem, it indicates its own operating state, for example, as described above. Ready terminal device ready signal E
Control signals such as R and the transmission request signal RS are ON / OFF controlled in response to a control command from the process control device.
Further, the process control device sends each of the control commands to the transmission device according to the control status of the control target device.

Therefore, since the transmission device does not send each control signal indicating the data transmission permission to the transmission target device only when the process control device can correctly receive the data, the process control device transmits the data from the transmission target device. Since data is transmitted only when it can be correctly accepted, the data transmission efficiency is increased.

Furthermore, since the device to be transmitted can send and receive data to and from the transmission apparatus of the present invention by the same transmission / reception procedure as the conventional transmission / reception procedure, the versatility of this data transmission system will not deteriorate. Absent.

In another invention, the process control device monitors the control signal state of the modem. Therefore, the transmission state of the transmission target device and the transmission state of the modem can be grasped, and the process control device can send the above-mentioned control commands in consideration of the situation of the other party.

[0032]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing a schematic configuration of a process monitoring device and a transmission device to which the data transmission system of the present invention is applied. The same parts as those of the conventional process control device and transmission device 7 shown in FIG. 5 are designated by the same reference numerals. Therefore, detailed description of the overlapping portions is omitted.

The overall view of the process control system and the arrangement diagram of the terminals 14a to 20b for each control signal of the transmission device 7 and the transmission target device 9 are the same as those of the conventional system shown in FIGS.

In the program memory 3 of the process control apparatus 1a of this embodiment, in addition to the control program for controlling the control-target equipment 8, data communication with the transmission-target equipment 9 is performed via the transmission apparatus 7a. The transmission task 30a is stored, and in the data memory 4, a transmission data memory 40 for storing various data to be transmitted to the transmission target device 9 is formed. Further, in the transmission control device 7a, in addition to the transmission control unit 70a, the transmission interface unit 71, and the transmission data memory 73, a modem control command memory 73 and a modem state memory 74 are provided.

The modem control command memory 73 stores and holds the terminal ready command ER and the transmission request command RS transmitted from the transmission task 30a of the process control device 1a. Further, in the modem state memory 74, terminals 14a, 15a, corresponding to the modem 12a on the self side shown in FIG.
The control signal states of 16a, 17a, 18a, 19a and 20a are stored and held.

Next, the operation of the process control device 1a and the transmission device 7a will be described. First, after the power of the entire system is turned on and the system is shifted to the initialization state, the transmission task 30a of the process control device 1a executes data transmission with the transmission target device 9 according to the flowchart shown in FIG.

The flow chart is started, and in P (program step) 1, for example, a control calculation process in one control cycle for the controlled device 8 is completed, and a waiting time occurs until the start of the next control cycle. Alternatively, when it is detected that the data transmission is required in the control arithmetic processing process and the state in which the data can be transmitted to the transmission target device 9 is detected, the ON command of the terminal device ready signal ER is written in the modem control command memory 73 of the transmission device 7a. (P
2).

On the contrary, when the control calculation process of the next control cycle is started and it is detected that the data from the transmission target device 9 is received, the appropriate process cannot be performed on this data (P3). The OFF command of the terminal device ready signal ER is written in the modem control command memory 73 of the transmission device 7a (P4). If the ON command has already been written, this ON command is rewritten to the OFF command.

In P5, when a data transmission request to the transmission target device 9 is generated, the transmission request command RS is written in the motif control command memory 73 of the transmission device 7a. Then, the signal states of the terminals 14a to 20a of the modem state memory 74 are read (P7). Data set ready signal D
R, carrier detection signal CD, and transmission permission signal CS are all O
If it can be confirmed that it is N (P8), the data to be transmitted is written in the transmission data memory 72 of the transmission device 7a (P9). Then, if other work exists, it is executed (P10).

Further, the transmission control section 70 of the transmission device 7a.
3a is obtained every time a minute time ΔT elapses after the power of the entire system is turned on and the system is shifted to the initialization state.
Execute the time interrupt flow process shown in. That is, when the ON command or the OFF command of the terminal device ready signal ER or the transmission request signal RS is set in the modem control command memory 73 by the transmission task 30a of the process control device 1a (Q1), it is an ON command or an OFF command. Judge (Q
2) Convert the signal state of the corresponding signal terminal 19a, 16a to the designated ON state or OFF state (Q3.
Q4).

Next, each terminal 14a for the modem 12a
Read the signal state of each control signal of ~ 20a (Q5),
The data is set in the modem status memory 74 (Q6). Therefore, the modem state memory 74 always has the latest terminals 14a.
The signal states of the control signals 20a to 20a are stored and held.

Further, the transmission controller 7 of the transmission device 7a.
When receiving the transmission command from the transmission task 30a of the process control device 1a, the data 0a reads out the data to be transmitted from the transmission data memory 72 and transmits it as the transmission data signal SD from the terminal 14a.

The transmission device 7a receives the data from the transmission target device 9 from the terminal 15a. In this way, the transmission device 7a transmits and receives the above-mentioned control signals, whereby the transmission task 30a of the process device 1 and the transmission target device 9 are transmitted.
Send and receive data to and from.

With such a data transmission method, even if the power of the entire system is turned on and the initial processing ends and the normal operation state is entered, the transmission control section 70a of the transmission apparatus 7a operates as a process control apparatus. Transmission task 3 of 1a
The terminal device ready signal ER at the terminal 19a is not turned on unless an ON command for the terminal device ready signal ER is input from 0a.

Therefore, the terminal 18 of the transmission target device 9 side
The data set ready signal DR of b never turns ON. Therefore, the transmission target device 9 is the transmission device 7a on the other side.
However, the data is not sent to the transmission device 7a side because it is judged that the transmission preparation is not completed yet.

Since the transmission request signal RS to the modem 12a is also turned on by the ON command from the transmission task 30a of the process controller 1a, the modem 12a does not shift to the reception standby state.

In this way, from the transmission device 7a to the modem 12
A terminal ready signal ER and a transmission request signal RS to the modem 12a transmitted to the transmission target device 9 side via a.
The ON / OFF control is executed not by the judgment of the transmission device 7a itself but by the judgment of the transmission task 30a of the process control device 1a.

Transmission task 30a of the process controller 1a
As shown in the flow chart of FIG. 2, the transmission device 7a is set at the optimum timing according to the control processing status of the control target device 8.
ON to terminal device ready signal ER and transmission request signal RS
A / OFF command is sent. Therefore,
If the process control device 1a is not ready to receive data, or if the process control device 1a can receive data but cannot immediately process the data, the device 9 to be transmitted does not send data or send a data communication request. Absent.

Therefore, useless data is prevented from being repeatedly transmitted to the modems 12a and 12b and the modem-dedicated signal cable 13. Moreover, since the transmission device 7a is different from the conventional transmission device 7 in the timing of sending each control signal, the conventional transmission target device 9 can be used as it is as the transmission target device 9 of the data transmission method. That is, it is not necessary to change the specifications when adopting the data transmission method of the present invention. Therefore, the data transmission method of the present invention can be directly applied to the transmission target device 9 such as a monitor device or a host system that has existed in the past, and the data transmission efficiency can be significantly improved without impairing versatility.

Further, the transmission task 30a of the process control device 1a turns on each control signal of the modem 12a on its own side.
Since the ON / OFF state can be easily grasped as necessary, it is possible to prevent the transmission target device 9 from transmitting data in the busy state, for example. Therefore, the effects described above can be further improved.

[0051]

As described above, according to the data transmission method of the process control device of the present invention, the transmission device is the transmission target depending on the status of the control processing for the control target device which is the original task of the process control device. Each control signal sent to the equipment is controlled. Therefore,
As for the device to be transmitted, by grasping the respective control signals, it is possible to grasp the transmittable / suspended state on the side of the process control device connected to the transmission device.

Therefore, while maintaining the control signal transmission / reception procedure of the conventional standard, wasteful data transmission / reception between the transmission device and the transmission target device can be reduced as much as possible, and the data transmission efficiency can be improved, and the process control device and the transmission device can be transmitted. The processing efficiency is improved for the target device, and the usability of the process control device can be improved.

Further, the process control device can easily grasp the control signal state of the modem as necessary, and as a result, the operating state of the transmission target device can be grasped. Therefore, the transmission in consideration of the operating condition of the transmission target device is performed. Data communication with the target device can be performed, and the above-described data transmission efficiency can be further improved.

[Brief description of drawings]

FIG. 1 is a block diagram showing a schematic configuration of a process control device and a transmission device to which a data transmission method according to an embodiment of the present invention is applied.

FIG. 2 is a flowchart showing the operation of a transmission task in the process control device to which the data transmission method of the embodiment is applied.

FIG. 3 is a flowchart showing the operation of a transmission device to which the data transmission method of the embodiment is applied.

FIG. 4 is a schematic configuration diagram of a general process control system.

FIG. 5 is a block diagram showing a schematic configuration of a process control device and a transmission device using a conventional data transmission method.

FIG. 6 is a diagram showing an arrangement of control signals and respective terminals exchanged between a general modem, a transmission device, and a transmission target device.

[Explanation of symbols]

1, 1a ... Process control device, 2 ... CPU, 3 ... Program memory (APM), 4 ... Data memory (DM), 5
... system bus, 6 ... input / output device, 7, 7a ... transmission device, 8 ... control target device, 9 ... transmission target device, 10 ... signal cable, 11a, 11b ... transmission signal cable, 12
a, 12b ... modem, 13 ... modem dedicated signal cable,
40, 72 ... Transmission data memory, 70, 70a ... Transmission control unit, 71 ... Transmission interface unit, 73 ... Modem control instruction memory, 74 ... Modem state memory.

Claims (2)

[Claims] 1. A transmission device and a modem are interposed between a process control device that controls the operation of a control target device and a transmission target device, and the transmission device receives a data communication command from the process control device. In a data transmission method of a process control device that performs data communication with the transmission target via the modem according to a procedure of transmitting and receiving a predetermined control signal, the transmission device transmits to the transmission target device via the modem. A control signal indicating its own operating state is transmitted based on a control command received from the process control device, and the process control device transmits the control command to the transmission device according to a control situation for the control target device. A data transmission method of a process control device, which is characterized in that 2. A transmission device and a modem are interposed between a process control device for controlling the operation of a control target device and the transmission target device, and the transmission device receives a data communication command from the process control device. In a data transmission method of a process control device that performs data communication with the transmission target via the modem according to a procedure of transmitting and receiving a predetermined control signal, the transmission device transmits to the transmission target device via the modem. A control signal indicating its own operating state is transmitted based on a control command received from the process control device, the process control device grasps the control signal state of the modem via the transmission device, and grasps this. A process control, characterized in that the control command is sent to the transmission device according to a control signal state and a control situation for the controlled device. Data transmission method of the apparatus.