JPH0139123B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a programmable logic controller system with distributed programs and serial execution.

It is well known that when performing sequence control using a programmable logic controller (hereinafter referred to as PLC), the number of input points and output points that can be handled is limited to a certain amount or less due to the response speed and other capabilities of the PLC. be.

On the other hand, some general sequence control systems sometimes require more input/output points than a normal PLC has. For such a large-scale system, the first thing to do is to use a large-scale PLC with high capacity.
It is possible to prepare a PLC. However,
Large PLCs generally have no marketability, so mass production is not effective and system costs increase.

Furthermore, if a single PLC handles a large number of input/output points in this way, if that PLC breaks down, all controls will become unavailable at the same time, which is not desirable in terms of dispersing risks. There is a problem.

As a second measure, it has been considered and implemented to operate a plurality of medium-sized to small-sized PLCs in parallel to control a large-scale system as a whole.

However, in conventional systems that operate multiple PLCs in parallel, in order to associate each PLC,
When transmitting the state of a specific input/output of a certain controller to another controller, the certain controller applies the state of the specific input/output to its own external output terminal according to its program, and the other controller A configuration is adopted in which the corresponding signal is taken in from its own external output terminal, which is wire-connected to the above-mentioned external output terminal. In other words, external input and output terminals originally provided for controlling external devices are used for sending and receiving input/output data.

Therefore, a considerable number of external input/output terminals are used to "associate" each other, and the number of external input/output terminals that can actually be used decreases, making it difficult to expand the system scale even though the number of controllers increases. Sexuality does not improve. Furthermore, if a complicated "association" is performed, the wiring between the input and output becomes complicated, making checking the wiring extremely troublesome, and changing the "association" is also not easy.

Therefore, the present applicant proposed the following as a means of transmitting the above-mentioned specific input/output status to other controllers.
A dedicated data input/output bus line (hereinafter referred to as the link bus) is used, and each PLC is equipped with a new
We are proposing PLC. According to this PLC, other
When transferring input/output data to the PLC,
It becomes unnecessary to use external input/output terminals, further improving system expandability.

A basic object of the present invention is to increase the program execution speed in a PLC equipped with the above-mentioned link bus and to solve the problem of so-called racing. In other words, the biggest advantage of a PLC equipped with this type of link bus is that it can execute a user program by referring not only to the contents of its own input/output memory, but also to the contents of the input/output memory of other devices. The point is that it can be done. Specifically, it is possible to construct an interlock circuit between one's own machine and another machine by referring to each other's input/output data.

However, when an interlock circuit is configured between the own machine and another machine in this way, each time there is an instruction in the user program that refers to the contents of the input/output memory of the other machine.
It becomes necessary to access the input/output memory of another device via the link bus. Therefore, when the number of instructions that refer to the contents of the input/output memory of other devices increases in the user program, compared to when the program is executed by referring only to the contents of the input/output memory of the own device, There is a problem in that processing time is significantly increased due to the delay time required to access the input/output memory of another device.

Therefore, the applicant first increased the capacity of the input/output memory of each PLC, and in addition to the capacity corresponding to its own input/output circuit, it also had the capacity to correspond to the input/output circuit of other machines. Prior to execution of a user program, the contents of the input/output memory of another machine are imported into the storage area of the input/output memory of the own machine for the other machine, so that when executing the user program, the input/output data of the other machine can be referenced. The company provides a PLC that speeds up program processing by eliminating the need to access the input/output memory of other machines each time an instruction to be executed is called.

According to this PLC, in the user program,
There is no need to access the input/output memory of another device each time there is an instruction that requires reference to the input/output memory of another device, but on the other hand, within one instruction execution cycle, the input/output memory of each device Since the contents of each of In the case where an interlock circuit is configured in which both output relays are always turned on or off alternately by inserting the relay in series in the energized path, the output relay of the own machine operates and its B contact turns off. However, the status is not transmitted to the input/output memory of other machines until one instruction execution cycle is completed, so there is a so-called racing problem in which each output relay, which should normally be turned on and off alternately, ends up turning on and off at the same time. arise. That is,
In the input/output memory of the own machine, in addition to the own machine area corresponding to the own machine's input/output circuit, there is also an other machine area corresponding to the other machine's input/output circuit, and prior to the execution cycle of each user program, By importing all the contents of the other machine's input/output memory into the other machine's area in the own machine's input/output memory, instructions that refer to the other machine's input/output memory can be read while the user program is running. By eliminating the need to access the input/output memory of other machines each time, it is possible to eliminate delays in program execution speed caused by the delay time of accessing the input/output memory of other machines. The drawback is that there are fewer changes in the input/output memory of other machines, which would not be a problem if the input/output memory of the other machine was accessed each time an instruction that referred to the input/output memory of another machine was read during execution. In both cases, the instruction is transmitted to the input/output memory area of the other machine with a delay of one instruction execution cycle, and this causes a problem in that racing occurs.

This invention was made to solve the above problem, and its purpose is to
When controlling a large number of input/output points using a PLC, it is no longer necessary to use the external input/output terminals of each device to transmit input/output data within each machine.
In addition, while each PLC is executing a user program, there is no need to access the input/output memory of other machines each time, and an interlock circuit as described above can be configured between the PLC and other machines. However, the goal is to prevent racing from occurring.

In other words, the program distributed/serial execution type programmable logic controller system according to this invention is a PLC system consisting of a plurality of PLCs connected to each other via a link bus so that the contents of input/output memory can be exchanged. Each PLC includes a machine number setting means for setting the machine number order of the PLC; a user program memory in which a user program is stored; an input circuit to which an external input signal is applied; an external output signal an input/output memory having an own machine area corresponding to the own machine's input/output circuit and an other machine area corresponding to the other machine's input/output circuit; Therefore, if the machine number order of the relevant PLC is set to the highest, prior to execution of the user program, synchronized with other machines, data from each other machine is stored in the input/output memory area of the own machine. Write the transferred input/output data for the other machine,
If the machine number order of the PLC is set to a value other than the highest, the input/output data in the own machine area of the own machine's input/output memory is synchronized with other machines before execution of the user program. set to top level
Input transfer means for transferring to the PLC: Writes all input/output data in the input/output memory of the PLC transferred from the next higher PLC in the machine number order to the input/output memory of the own machine, and Refers to the input/output data, executes the user program of the own machine, rewrites the contents of the own machine's input/output memory with the execution result, and then moves the rewritten contents of the input/output memory one level lower in the machine number order. a program execution means for transferring the program to the PLC of the PLC; if the machine number setting of the PLC is set to the lowest by the machine number setting means, execution of the user program of the PLC is executed prior to the input/output refresh; When the contents of the output area for each other machine rewritten by are transferred to the PLC of the corresponding other machine, and the machine number ranking is set to other than the lowest by the machine number setting means, is an output transfer means for writing the output data for own machine transferred from the lowest PLC into the own machine output area of the input/output memory of the own machine prior to the input/output refresh; the above machine number setting; If the machine number ranking of the PLC is set to the lowest by any means, the PLC
The contents of the own machine's output area of the own machine's input/output memory that have been rewritten by the execution of the user program are
At the same time, the input data from the input circuit of the own machine is written to the own input area of the input memory of the own machine, and the machine number setting means sets the machine number order of the PLC. is set to a value other than the lowest level, the contents of the own device output area of the own device's input/output memory rewritten by the output transfer means are transferred to the own device's output circuit, and
The present invention is characterized by the following: an input/output refresh means for writing input data from an input circuit of the own machine into an input area of an input/output memory of the own machine;

Hereinafter, a preferred embodiment of the present invention will be described in detail with reference to the accompanying drawings.

Figure 1 shows the program distribution and
1 is a block diagram showing the electrical configuration of a serially executed programmable logic controller system. FIG. As shown in the figure, this PLC system is constructed by connecting a plurality of PLCs to each other via a link bus 1 and a link bus interface 10. Each PLC has a user program memory 2 in which a user program is stored, an input circuit 3 to which an external input signal is transmitted, an output circuit 4 to send an external output signal, and a capacity larger than that of the input/output circuits 3 and 4. Input/output memory with large capacity 5
and an instruction execution means for sequentially executing the instructions in the user program memory 2 at high speed, performing a logical operation based on the data in the input/output memory 5, and writing the operation result in the input/output memory 5;
The input/output updating means writes the input data of the input circuit 3 to a predetermined area of the input/output memory 5, and transmits the output data of the predetermined area of the input/output memory 5 to the output circuit 4. . Further, the above-mentioned instruction execution means and input/output updating means are constituted by a CPU 6 mainly composed of a microprocessor and a ROM.

CPU6 via switch interface 7
The machine number setting switch 8 connected to the machine number setting switch 8 is used to set the machine number order or set the machine number order when each PLC is operated as a host or a guest as described later. In the working memory 9, as shown in FIG. 2, there are provided an own machine register and an other machine status register. These registers are used to store the set status when each PLC is set as a guest or host, as described later.The own machine register stores the machine number of each PLC, and the other machine status register The machine number order of all the PLCs that make up this system is stored.

In the input/output memory 5, as shown in FIG. 3, in addition to input/output areas corresponding to the input circuit 3 and output circuit 4 of the own machine, input/output areas corresponding to the input/output circuits of other machines are provided. ing. In addition, the second
What is shown in the figure and Fig. 3 is the case where this system is configured with three PLCs, and #1, #2, and #3 shown in each input/output memory are #1 machine and #3, respectively. These are input/output areas corresponding to the input/output circuits of #2 and #3 machines, respectively.

Next, FIG. 4 shows a part of the system program stored in the ROM in the CPU of each PLC in order to control the operation of this PLC system. Furthermore, FIG. 5 is a state transition diagram showing how the contents of each register in the working memory change and the state of change of data in each input/output memory as the system program shown in FIG. 4 is executed. be.

According to these figures 4 and 5, this PLC
Systematically explain the operation of the system. In the following description, it is assumed that this system is configured by three PLCs.

The operation of the PLC according to the present invention is largely comprised of five cycles: an initial cycle, a 1N cycle, an execution cycle, an OUT cycle, and an I/O refresh cycle.

When initial processing steps 1A and 1B are executed in the host machine and the guest machine, respectively, an initial cycle is executed as shown in (1) of FIG. This initial cycle first sets the contents of machine number setting switch 8 in each PLC.
Imported into CPU 6 via interface 7,
Then, the contents are stored in the register of each machine. Next, the contents stored in the own machine register of each machine are sequentially taken into the other machine status register of the host machine (#1) and arranged in accordance with the machine number order. Next, the contents of the other machine status register of the host machine are sequentially transferred to the other machine status registers of machines #1 and #3. As a result, when the initial cycle ends, the contents of the other machine status registers of each machine become the same.

Next, steps 2A and 3 are performed on the host machine.
When steps A and 4A are executed and steps 2B, 3B, and 4B are executed on the guest machine, the IN cycle of the system is executed. In this IN cycle, as shown in Figure 5 (2), #2, #3
Only the contents of the input/output area for each machine are
Transferred to the corresponding area of #1 machine. That is, the #2 input/output area of the #2 machine and the #3 input/output area of the #3 machine are transferred to the respective corresponding areas of the #1 machine.

Next, on the host machine, step 5A, 6
A, 7A, 8A and 9A are executed and steps 7B, 8B, 9B, 10 are executed on the guest machine.
When B, 11B, 12B, 13B and 14B are executed, the execution cycle of the system is completed. In this execution cycle, the user program is first sequentially executed in machine #1 based on the contents of each input/output data taken in in the IN cycle. When the execution of machine #1 is completed, the contents of the input/output memory at that time are transferred to machine #2, and machine #2 then uses the contents of the input/output data transferred from machine #1. The user program is executed. When the execution of the user program is completed in the #2 machine in the same manner, the contents of the input/output memory which are the execution results are then transferred to the #3 machine. Then, in the #3 machine, the user program is executed in the same way based on the contents of the input/output data transferred from the #2 machine, and when the execution is completed, the contents of the input/output memory of the #3 machine are executed. will be transferred again to machine #1.

Next, steps 15A and 16 are performed on the host machine.
When steps A and 17A are executed and steps 15B, 16B, 17B, 18B and 19B are executed in the guest machine, an outcycle is performed as shown in FIG. 5(4). In this outcycle, the contents of the input/output data of the #3 machine, which is the final machine, are sequentially transferred to the #1 and #2 machines. In this example, when transferring input/output data from machine #3 to machines #1 and #2, only the input/output data area necessary for each machine is transferred. In other words, when transferring from machine #3 to machine #1, since it is done at the end of the aforementioned execution cycle, these input/output data are not transferred.On the other hand, from machine #3 to machine #2 When transferring the input/output data to the destination, the area corresponding to the #2 machine is transferred.

Next, step 20A is executed in the host machine, and step 20B is executed in the host machine.
When this is executed, an I/O refresh cycle is performed as shown in FIG. 5(5). At the start of this I/O refresh cycle, the contents of the area for the own machine in the output memory of each machine are always in the latest state. As a result, if the contents of the input/output area of the area for the own machine are transferred to the output circuit 4 in the I/O refresh cycle, the above-mentioned racing problem will not occur. In other words, for this PLC system,
Each time a user program finishes executing on each machine, the input/output memory is transferred to the next machine, and each next machine executes the user program based on the transferred input/output data. Therefore, for the entire PLC system, it is the same as if all user programs were executed by one PLC, which is a problem in conventional PLC systems equipped with multiple devices. This solves the problem that the underlying I/O data becomes inconsistent when a user program is executed, and as a result, even if an interlock circuit is configured between multiple machines, racing will not occur. That's why.

As is clear from the above description of the embodiments, the program distributed/serial execution type programmable logic controller system according to the present invention has the following features:
A PLC system consisting of a plurality of PLCs connected to each other via a link bus so that the contents of input/output memory can be exchanged; each PLC has a function for setting the machine number order of the PLC. A program setting means; A user program memory in which a user program is stored; An input circuit to which an external input signal is applied; An output circuit to send an external output signal; An area corresponding to the input/output circuit of the own machine In addition, an input/output memory including an other device area corresponding to the input/output circuit of another device; Prior to executing the program, synchronize with other machines, write the input/output data for the other machine transferred from each other machine to the other machine area of the own machine's input/output memory,
If the machine number order of the PLC is set to a value other than the highest, the input/output data in the own machine area of the own machine's input/output memory is synchronized with other machines before execution of the user program. set to top level
Input transfer means for transferring to the PLC: Writes all input/output data in the input/output memory of the PLC transferred from the next higher PLC in the machine number order to the input/output memory of the own machine, and Refers to the input/output data, executes the user program of the own machine, rewrites the contents of the own machine's input/output memory with the execution result, and then moves the rewritten contents of the input/output memory one level lower in the machine number order. a program execution means for transferring the program to the PLC of the PLC; if the machine number setting of the PLC is set to the lowest by the machine number setting means, execution of the user program of the PLC is executed prior to the input/output refresh; When the contents of the output area for each other machine rewritten by are transferred to the PLC of the corresponding other machine, and the machine number ranking is set to other than the lowest by the machine number setting means, is an output transfer means for writing the output data for own machine transferred from the lowest PLC into the own machine output area of the input/output memory of the own machine prior to the input/output refresh; the above machine number setting; If the machine number ranking of the PLC is set to the lowest by the means, the contents of the own machine's output area of the own machine's input/output memory that have been rewritten by the execution of the user program of the relevant PLC are automatically At the same time, the input data from the input circuit of the PLC is written to the own input area of the input memory of the own machine, and the machine number setting means sets the machine number order of the PLC. If it is set to other than the lowest level, the contents of the output area of the own machine's input/output memory rewritten by the output transfer means are transferred to the own machine's output circuit, and the contents of the own machine's output area of the own machine's input/output memory are transferred to the own machine's input circuit. The present invention is characterized by the following: input/output refresh means for writing input data from the machine into the input area of its own input/output memory; In comparison, when transferring input/output data between each machine, there is no need to occupy external input/output terminals, and when referring to input/output data of other machines, the input/output memory of the other machine can be accessed each time. Program execution time can be shortened since there is no need to do this, and even when an interlock circuit is configured between the own machine and another machine, there are advantages such as no racing occurring. It has the following characteristics.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing the electrical configuration of the system of the present invention, FIG. 2 is a diagram showing the contents of the own machine register and other machine status register shown in the working memory of FIG. 1, and FIG. is a block diagram showing the configuration in the input/output memory, FIG. 4 is a flowchart showing the contents of the system program that defines the operation of this system, and FIG. 5 is a flowchart showing the contents of the system program that defines the operation of this system. FIG. 4 is a state transition diagram showing a state in which the contents of the own machine register in the working memory, the other machine status register, and the area for each machine in the input/output memory change. 1... Link bus, 2... User program memory, 3... Input circuit, 4... Output circuit, 5...
Input/output memory, 6... CPU, 7... Switch interface, 8... Machine number setting switch, 9
... Working memory, 10... Link bus interface.

Claims (1)

[Claims] 1. A PLC system consisting of a plurality of PLCs connected to each other via a link bus so that the contents of their input/output memories can be exchanged; machine number setting means for setting the machine number order; a user program memory in which a user program is stored; an input circuit to which an external input signal is applied; an output circuit to send an external output signal; an input/output circuit of the own machine. In addition to the own machine area corresponding to the own machine area, the input/output memory has an other machine area corresponding to the input/output circuit of the other machine; and the machine number setting means sets the machine number order of the PLC to the highest. If the user program is executed, the input/output data for the other machine, which is transferred from each other machine, is synchronized with the other machine and transferred to the other machine area of the own machine's input/output memory. writing,
If the machine number order of the PLC is set to a value other than the highest, the input/output data in the own machine area of the own machine's input/output memory is synchronized with other machines before execution of the user program. set to top level
Input transfer means for transferring to the PLC: Writes all input/output data in the input/output memory of the PLC transferred from the next higher PLC in the machine number order to the input/output memory of the own machine, and Refers to the input/output data, executes the user program of the own machine, rewrites the contents of the own machine's input/output memory with the execution result, and then moves the rewritten contents of the input/output memory one level lower in the machine number order. a program execution means for transferring the program to the PLC of the PLC; if the machine number setting of the PLC is set to the lowest by the machine number setting means, execution of the user program of the PLC is executed prior to the input/output refresh; When the contents of the output area for each other machine rewritten by are transferred to the PLC of the corresponding other machine, and the machine number ranking is set to other than the lowest by the machine number setting means, is an output transfer means for writing the output data for own machine transferred from the lowest PLC into the own machine output area of the input/output memory of the own machine prior to the input/output refresh; the above machine number setting; If the machine number ranking of the PLC is set to the lowest by any means, the PLC
The contents of the own machine's output area of the own machine's input/output memory that have been rewritten by the execution of the user program are
At the same time, the input data from the input circuit of the own machine is written to the own input area of the input memory of the own machine, and the machine number setting means sets the machine number order of the PLC. is set to a value other than the lowest level, the contents of the own device output area of the own device's input/output memory rewritten by the output transfer means are transferred to the own device's output circuit, and
A program distributed/serial execution type programmable logic controller system comprising: an input/output refresh means for writing input data from an input circuit of the own machine into an input area of an input/output memory of the own machine; and;