JPH09135260A - Hierarchical method for programmable logic controller by network - Google Patents

Abstract

PROBLEM TO BE SOLVED: To eliminate a delay in program execution by avoiding trouble and mistake for program description in a relay station by applying hierarchical processing to a network tying plural relay stations each having a CPU and a communication module. SOLUTION: Relay stations PLC(programmable logic controller) 3-6 whose station numbers are S0-3 belong to a higher layer communication network 1 and relay stations PLC 3, 7, 8 whose station numbers are S0, 4, 5 belong to a lower layer communication network 2. Since the relay station PLC 3 belongs to the two communication networks, the two station numbers are the same as S0. Each PLC is made up of a CPU for execution of a user program and for I/O control, a communication module and an I/O module. Thus, in the case of sending/referencing data between PLCs, it is executed by using a user program of an object PLC only and trouble or mistake of describing a program in the relay station is avoided. Furthermore, a delay by one period of execution of the user program is eliminated.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of layering a programmable logic controller (hereinafter abbreviated as PLC) using a communication network.

[0002]

2. Description of the Related Art FIG. 9 is a communication network configuration diagram showing an example of a conventional technique, which is a method of hierarchizing PLCs in network units by a connection configuration of a plurality of PLCs and a plurality of communication networks. That is, the relay station PLC 113 is
Connected to two different communication networks 111 and 112, the other regular stations PLC 114-118 are connected to only one of the communication networks. In such a configuration, PLs that are layered on different communication networks 111 and 112
C 114 to 118 have a hierarchical relationship of upper and lower levels.

Each PLC has a link memory for storing data (or link data) transmitted between PLCs having the same hierarchical relationship, and FIG. 10 shows the configuration of the link memory of the PLC layered in each hierarchy. . Link memory is own station PLC
, And the reception data area of the other station PLC, and are updated (or link refresh) at a cycle set by the user. The relay station PLC 113
Has two layers, and thus has a link memory for storing independent link data for each layer. 11 is an upper layer PLC link memory of each normal station PLC 114, 115, 116 by the communication network 111, and 12 is a relay station P of the relay station 113.
LC link memory, 13 is a lower layer PLC link memory of each normal station 118, 117 by the communication network 112.

[0004]

In the conventional example, since the link data is independent in the PLCs layered in different layers, there is a problem when the following request occurs. (1) When data is transmitted between PLCs in different layers, in the relay station PLC, it is necessary for the user to preset the correspondence of the link data to be transferred between the link memories for each layer. It was (2) Alternatively, it is necessary to insert a data transfer instruction between link memories in the user program executed by the relay station PLC.

In the above item (1), there is a troublesome setting imposed on the user, and the omission or mistake of the setting may lead to malfunction of the applied system. In the above (2), since the delay of one execution cycle of the user program is always inserted while the data is transferred between different layers, the delay of the transfer time must be taken into consideration.

[0006]

SUMMARY OF THE INVENTION An object of the present invention is to solve each of the above-mentioned problems by hierarchizing each PLC.
However, it is to enable mutual data transmission. Therefore, each PLC is provided with a link memory that stores the link data of all PLCs. Then, in a relay station in which two communication networks, that is, layers are connected, the link data is received from the PLCs connected to the respective communication networks, and the link data is combined and transmitted to each PLC. The minute link memory is refreshed with the same link data.

[0007]

By the above-described means, each layered PLC can have the same link data of all PLCs, so that the user can layer PLCs in any layer.
In the above, a program for transmitting data to and from PLCs in different layers can be easily created, and it is not necessary to set the correspondence of the link data in the relay station and to describe the data transfer command between the link memories.

[0008]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing an embodiment of the present invention, and shows a hierarchical structure including six PLCs 3 to 8 and two communication networks (1) and (2). Note that NO and N1 in the figure represent the identification number of the communication network, and S
0 to S5 represent PLC station numbers. In FIG. 1, the relay station PLC3 has two stations for connecting to two communication networks. In the example of the figure, in order to make the link data of each PLC the same, the two station numbers of the relay station PLC3 are set to the same S0, and the station number S that does not overlap with other normal stations PLC is used.
1 to S5 are given. In order to improve reliability, one communication network has a double ring configuration by connecting each PLC with a two-wire optical cable. The communication is based on the token passing method.

FIG. 2 is a block diagram showing the configuration of the PLC. Each of the PLCs 3 to 8 executes a user program and I
CPU 20 for controlling I / O, communication modules 30 and 40 for transmitting / receiving communication data via a communication network, I / O
It is composed of an O module group 50 and is connected by an I / O bus 60. The relay station PLC3 is a communication module.
It requires both 30 and 40, and the communication module 30 closer to the CPU is for the upper network, that is, for the upper layer,
The other communication module 40 is set by the CPU for the lower network, that is, the lower layer. Further, in the normal station PLC, only the communication module 30 from the CPU is required, and an I / O module can be applied to the vacant portion.

FIG. 3 is a block diagram showing a main part of the CPU 20 shown in FIG. 2. The microprocessor 21 executes the user program stored in the RAM 23. Link memory
24 is accessible from the microprocessor 20 and is accessible from the communication module 30 or 40 via the I / O bus interface 25. Note that the I / O bus 60 of FIG.
The link memory 24 also has an arbitration function based on the first-come-first-served basis.

FIG. 4 is a block diagram showing a main part of the communication module shown in FIG.
Set the identification number of the network to which C is connected. The station number setter 38 sets the station number of the PLC in the network. The PLC having the smallest station number in one communication network functions as a master station of the network, and the other PLCs function as slave stations. In the example of FIG. 1, the relay station PLC3 also has the function of a master station for each communication network. Dual port RAM
Reference numeral 34 is a memory used for receiving initial settings and request commands from the CPU 20 and for displaying the status of the communication module and communication network.

FIG. 5 is an example of a memory map showing the link memory 24 of the CPU 20 and the link memory address table initialized by the CPU on the dual port RAM 34 of the communication module 30 or 40. There is an area for storing link data for all N stations that are hierarchically structured, and the communication module accesses the link memory based on the link memory address table.

A link refresh operation in which the link memory of each PLC is shared by the link data of all PLCs in the above configuration will be described. The CPU 20 of each PLC asynchronously repeats the operation of the program created by the user and the I / O rear fresh control at different cycles. After the pumegram calculation for each cycle, a link refresh request is output to the communication module. Since the relay station PLC3 has two upper and lower networks, that is, communication modules for layers, it outputs a link refresh request to each.

As shown in the flow chart of FIG. 6, the communication module that has received the request writes the link data of another station in the corresponding area of the link memory of the CPU if it has received new link data from the communication network. . (A, B) The link data for the own station is read from the corresponding area of the link memory of the CPU. (C) Output a processing end notification to the CPU. (D) Prepare to send the link data for your own station. (E)

Upon receipt of the processing end notification, the CPU shifts to I / O refresh control. Next, the communication module for the upper network of the relay station PLC is the normal station PLC connected to the upper network.
The link data of (4) to (6) is received and read into the corresponding area of the link memory of the CPU. The link data received by the normal station PLC (7), (8) connected to its own station and the lower network
The link data for all the stations to which the link data received from is added is transmitted to the normal stations PLC (4) to (6).

On the other hand, the communication module for the lower network of the relay station PLC is the normal station PLC connected to the lower network.
The link data of (7) and (8) is received and written in the corresponding area of the link memory of the CPU. Link data for all stations, in which the link data received from the normal station PLCs (4) to (6) connected to the own station and the host network are added to the link data received in the normal station PLC (7), Send to (8).

The PLC communication module other than the relay station transmits the link data for its own station based on the link data transmission request from the relay station. Based on the link data reception request from the relay station, the link data for all stations is received. Through the above operation, the link memory on the CPU of each layered PLC is refreshed with the same link data. Therefore, it is possible to directly refer to the link data of the PLC layered in a different layer by the user program of the PLC layered in a certain layer.

FIG. 7 is a block diagram showing a second embodiment of the present invention, and can be applied as it is to an example in which two or more lower networks are connected to the upper network. In this example, there are multiple relay stations when focusing on the higher-level network, but in the order in which the circulating tokens are obtained,
By receiving and transmitting the same link data as described above, the contents of the link data of each PLC become the same.

FIG. 8 is a block diagram showing a third embodiment of the present invention. If the communication module of each PLC is replaced with a module corresponding to a coaxial cable instead of an optical cable, the PLC according to the present invention is hierarchized. Can also be applied to a bus type communication network.

[0020]

As described above, according to the present invention, when data is transmitted or referred to between PLCs layered in different hierarchies, only the user program of the target PLC can be used. As described above, the trouble of setting the relay station PLC and writing a program,
You can eliminate mistakes. Further, when the data transfer instruction is described in the relay station, the delay caused by one cycle of user program execution can be eliminated.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of an embodiment.

FIG. 2 is a block diagram showing a configuration of a PLC.

FIG. 3 is a block diagram showing a main part of a CPU.

FIG. 4 is a block diagram showing a main part of a communication module.

FIG. 5 is a memory map showing a link memory and its address table.

FIG. 6 is a flowchart showing a process performed first by a communication module which receives a link refresh request from a CPU.

FIG. 7 is a block diagram showing a configuration of another embodiment.

FIG. 8 is a block diagram showing a configuration of another embodiment.

FIG. 9 is a block diagram showing a configuration of a conventional example.

FIG. 10 is a memory map showing a configuration of a conventional link memory.

[Explanation of symbols]

 1 Upper network 2 Lower network 3 Relay station PLC 4 Normal station PLC 5 Normal station PLC 6 Normal station PLC 7 Normal station PLC 8 Normal station PLC 11 Upper layer PLC link memory 12 Relay station PLC link memory 13 Lower layer PLC link memory 111 Upper Network 112 Lower network 113 Relay station PLC 114 Normal station PLC 115 Normal station PLC 116 Normal station PLC 117 Normal station PLC 118 Normal station PLC

Claims (1)

[Claims] 1. In a method of hierarchizing a plurality of programmable logic controllers by a plurality of communication networks, each programmable logic controller is provided with a link memory for storing link data of all programmable logic controllers, and refreshed with the same data. In this way, it is possible to directly transmit data between programmable logic controllers layered in different layers, and a method for layering a program logic controller by a network.