JPH0828727B2 - Programmable controller network communication method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention relates to a programmable controller (hereinafter, referred to as a PC) as a node, in which a plurality of PCs are connected to each other in a PC network. The present invention relates to a communication method of a PC network that communicates with each other by a token passing method.

[Prior Art] The token passing method is a communication method in which a control packet called a token is circulated (passed) in a system network and a node (communication device) receiving the control packet obtains a transmission right.

As is well known, a PC, unlike a terminal dedicated to communication, has an original task other than communication, which is a sequence controller and must be performed by itself. Therefore, in addition to the command / response sequence (general-purpose sequence) performed in a normal communication network, each PC performs communication while performing the mask given to itself, and ( A command / response sequence (dedicated to PC link) (hereinafter referred to as a dedicated sequence) is required. As the general-purpose sequence of the PC network, for example, the communication between the sequencer and the monitor corresponds thereto. Further, as the dedicated sequence, for example, the I / O allocation instruction transmitted from the PC that is going to transmit the data to the PC that should receive the data and the response thereto correspond thereto.

In the following description, communication between PCs refers to a dedicated sequence, and therefore commands and responses refer to commands and responses in a dedicated sequence.

Conventionally, when communication between PCs is performed by token passing in a PC network, the communication procedure is such that a master (temporary master) PC arbitrarily defined as necessary and a partner with which the master PC sends a command. It was a system that communicates with the slave PC, which is the destination, on a one-to-one basis. That is, the master PC creates a command to send to the slave PC, and when the token is held, the slave PC sends the command.
Send to PC. On the other hand, when the slave PC receives the command, it creates a response, and when the token is held, it returns the response to the master PC.

FIG. 2 is a diagram showing an example of a command / response sequence between PCs in a PC network to which this conventional communication method is applied.

In this example, the system network is n node PCs.
It is composed of 1, 2, ..., N−1, n and a transmission medium (link) that connects these nodes. The vertical axis of FIG. 2 is the time axis. Tokens are PC1, PC2, ..., PCn-1, PCn, PC1, PC2, ...
Patrol in the order of.

Here, the master PC is determined according to the needs at that time. Now, when the command transmitted from PC1 to each slave PC2,3 ..., n is the same when PC1 is set as the master PC, the command / response sequence is as follows. First, PC1 creates a command,
Wait for the tokens to cycle. When PC1 holds the token, it sends a command to PC2, PC3 ... Until the token holding time expires. In the example of Fig. 2, the command is PC3
The token holding time has expired after being sent to. On the other hand, when PC2 and PC3 receive the command, they respectively create a response and wait for the token to circulate. When the token is passed, PC2 returns a response to PC1, and PC1 processes the response. next,
When the token is passed to PC3, PC3 returns a response to PC1, and PC1 processes the response received from PC3. The tokens will be handed over to PC4, ..., PCn in sequence,
Since commands are not sent from PC1 to these PCs,
No response is returned to PC1 at each token holding time.

In this way, when the token is circulated once and passed to PC1 again, PC1 sends a command to PC4 and PC5 (in the example of Fig. 2, PC1 has two slave PCs at one token holding time).
Command is transmitted to n, and n is an odd number. ), The same sequence as in PC2, PC3 is executed (not shown). At this time, the token circulates to PC2, PC3, PC6, ..., PCn, but no response is returned from these slave PCs.

By repeating such a sequence, the token becomes (n-
3) / 2 rounds and when it is handed to PC1 again, PC1
1, the command is sent to PCn, the same processing as described above is performed, and the response processing from all slave PCs is completed.

[Problems to be Solved by the Invention] In the conventional communication method of the PC network described above, when the same command is transmitted to all slave PCs, the master PC that creates the command is as many as the number of partner PCs existing in the PC network. You must send the command. as a result,
If the number of PCs is large and commands cannot be sent to all slave PCs within one token holding time, the command
In order to complete the response sequence, it is necessary for the token to make several rounds, which has the drawback of reducing the efficiency of communication processing.

[Means for Solving the Problems] A communication method of a PC network according to the present invention is configured by connecting a plurality of PCs with each PC as a node.
In the communication method of the PC network in which each of the PCs of the PC network communicates with each other by the token passing method, the master PC, which is arbitrarily determined as necessary, sends the command by the broadcast method while holding the token. Each slave PC sends a response to the master PC when it has a token.

[Operation] When sending the same command to all slave PCs, the master PC creates a dedicated command in the PC link, and when it holds a token, broadcasts that command to all slave PCs (simultaneous broadcast, that is, A communication method in which it is necessary to receive the information without specifying the recipient of the transmitted information, and all the recipients who have the right to receive the information receive the information). When the slave PC receives the command, it creates a response, and when the token is held, it returns the response to the master PC.

Therefore, even if the number of PCs increases, the command transmission from the master PC is completed in one token holding time, so the sequence of command response is 1 token.
It is completed when the circuit is circulated, and the efficiency of communication processing can be improved.

Example Next, an example of the present invention will be described with reference to the drawings.

FIG. 1 is a diagram showing an embodiment of a command / response sequence between PCs in a PC network to which the communication method of the present invention is applied.

Also in this embodiment, the PC network is composed of n PCs 1, 2, ..., N similarly to the PC network of FIG. 2, and PC1 is set as the master PC. Also, the tokens are PC1, PC2,… PC
It cycles in the order of n−1 and PCn.

PC1 creates a dedicated command in the PC link to send to all slave PCs, waits for the token to come around, and when it holds the token, broadcasts the created command to all slave PCs2,3, ..., n- Send to 1, n. When each slave PC2,3, ..., n-1, n receives the command, it creates a response and waits for a token to come around. When PC2 holds the token, it returns the created response to PC1. When PC1 receives the response, it performs response processing. The same applies to PC3 to PCn.

[Effect of the Invention] As described above, the present invention broadcasts when the same command is sent from a specified PC to all other PCs in the case of exchanging data between PCs in the PC network using the token passing method. By transmitting by the method, the command can be transmitted to each PC in one token holding time, and as a result, the efficiency of communication in the PC network can be improved.

[Brief description of drawings]

FIG. 1 shows a PC network to which the communication method of the present invention is applied.
FIG. 2 is a diagram showing an example of a command / response sequence between PCs, and FIG. 2 is a diagram showing an example of a command / response sequence between PCs in a PC network to which a conventional token passing system is applied.

Claims (1)

[Claims] 1. A programmable controller network comprising a plurality of programmable controllers, each programmable controller being a node, wherein any two programmable controllers are independently communicatively connected to another programmable controller. However, in the communication method of the programmable controller network that performs mutual communication by the token passing method, when communicating from any programmable controller in control operation to another programmable controller in control operation, that programmable controller is temporarily The master programmable controller is defined as the master programmable controller, and the temporary master programmable controller A dedicated controller network communication that transmits a dedicated command in the programmable controller link by the broadcast mode, and each slave programmable controller returns a response to the master programmable controller when holding the token. Method.