JPH0724407B2 - Communications system - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial field of application) The present invention relates to a right of use of a communication medium in which a plurality of communication stations including a central processing unit and a communication control unit are connected to each other in a bus shape by a communication medium. The present invention relates to a communication system in which communication is performed between communication stations while sequentially transmitting and receiving (tokens), and more specifically, each communication station has a configuration in which a central processing unit and a communication control unit are duplicated, and a standby side The present invention relates to a communication system capable of efficiently performing communication with the central processing unit.

(Prior Art) Conventionally, a communication system of a token bus system is known in which communication between respective communications is performed while sequentially exchanging the right to use a communication medium.

FIG. 5 is a structural conceptual diagram of such a communication system. In the figure, LN is a communication medium, N1, N2 ... Nn are communication media
It is a communication station connected to the LN in a bus shape. Each communication station is configured to perform communication between each communication station while sequentially exchanging usage rights (tokens) of the communication medium LN.

In such a communication system, each communication station has a standby redundant system configuration in which a central processing unit and a communication control unit are duplicated, and when performing communication with the central processing unit on the standby side, the active side The communication control device of 1 transmits a token to the communication control device on the standby side of its own station, so that the communication control device on the standby side obtains the right to use the communication medium and executes the communication.

In such a communication system, in each communication station connected to the communication medium, if the active side always turns the token to the standby side, it takes a long time for the token to go around.

Therefore, some communication stations are provided with a switch indicating whether or not the token needs to be turned to the standby side, and turn the token only when the switch is turned on.

(Problems to be Solved by the Invention) However, in such a conventional system, in order to change the communication state in each communication station, there is a switch for performing communication operation to the standby side. There was the annoyance of having to go to the place where the communication station was installed and change the switch each time.

The present invention has been made in view of such problems, and an object thereof is to enable remote control of whether or not to send a token to a standby side at each communication station, and to improve workability. It is to realize a good communication system.

(Means for Solving the Problems) FIG. 1 is a basic configuration block diagram of the present invention. In the figure, N1 ... Nm ... Nn are a plurality of communication stations connected to the communication medium LN in a bus shape. 1A, 1B at each communication station
Is a central processing unit, and 2A and 2B are communication control units, which are duplicated in configuration.

In each of the communication stations N1 ... Nm, A1 and A2 are standby side communication permission signal lines that connect the two communication control devices 2A and 2B and exchange the standby side communication permission signal with each other.

In the two communication control devices 2A and 2B, when 3A and 3B receive a standby communication permission command from another station, they output a standby permission signal to the other communication control device through the communication line and Communication control means for transmitting the token to the communication control device on the standby side when the token to the station is received, 4
A and 4B are waiting to perform a communication operation when their own communication control device is waiting and there is a standby side permission signal output from the communication control device on the active side, and when a token from the active side to the standby side is received Communication control means.

(Operation) A plurality of communication stations perform communication between the communication stations while sequentially exchanging the usage right (token) of the communication medium LN.

When communication to the stand-by side is required, the working-side communication control means receives a stand-by side communication permission command indicating that, outputs a stand-by side communication permission signal, and sends a token from the working side to the stand-by side. Is sent. The standby-side communication control means receives the standby-side communication permission signal, and executes the communication when the token arrives at itself.

Embodiments Embodiments of the present invention will be described in detail below with reference to the drawings.

FIG. 2 is a configuration block diagram showing an embodiment of the present invention. Here, only one communication station is shown as a representative.
The same parts as those in FIG. 1 are designated by the same reference numerals.

In one communication station N1, 11A and 11B are physically connected to a communication medium LN and are transmission / reception means for transmitting / receiving, and 12A and 12B are media. The access control means includes a token sending means for sending and receiving a token for controlling the right to use the communication medium LN.

In the standby side communication control means 4A, 4B, 13A, 13B, when inputting the standby side communication permission signal output from the active side communication control means, when receiving the token from the active side to the standby side,
When the standby side communication permission signal does not exist, the communication means for performing the communication operation, when the active side fails, for example, when the standby side communication active signal does not exist, and the standby side becomes active, the transmission request being executed until then is aborted (abort). This is a communication request abort means.

The operation of the device configured as described above will be described below.

FIG. 3 is an operation conceptual diagram showing signals on the communication medium LN when the active side communicates.

The token circulates to the working side of each communication station N1, N2, N3 ...
It does not visit the standby side of each communication station.

In this state, for example, in the communication station N2, the standby communication request abort means 5B has no standby communication station permission signal to the standby communication request abort means 5B, and therefore aborts the internal communication request.

FIG. 4 is an operation conceptual diagram showing signals on the communication medium LN when the standby side communicates. Here, in advance, for example, one of the communication stations issues a standby-side communication permission command to the communication station N2 via the communication medium LN, and the communication station N2, based on this, the active-side communication control means. It is assumed that 3A outputs a standby communication permission signal to the standby side via the signal line A1.

First, the communication station N1 sends a token to the communication station N2 as shown in (a). Communication station that received this token
As for N2, the communication control means 3A on the working side first executes communication using the communication medium LN as shown in (b). next,
The communication control means 3A in the communication station N2 uses the token for the standby side in its own communication station N2 as a communication medium, as shown in (c).
Send out via LN. The communication means 13B on the standby side, which has received this token, executes communication using the communication medium LN, as shown in (d), because the communication authorization signal on the standby side already exists. Then, as shown in (e),
Send the token to the working side of N3.

(Effect of the Invention) As described in detail above, according to the present invention, in a normal state, the token is circulated only to the working side of each communication station, and when communication to the standby side is required, the communication is performed. By sending a standby communication permission command from one of the communication stations to the station, communication with the standby side becomes possible. Therefore, according to the present invention, it is possible to remotely control whether or not to send the token to the standby side, and to realize a communication system with good workability.

[Brief description of drawings]

FIG. 1 is a block diagram showing a basic configuration of the present invention, FIG. 2 is a configuration block diagram showing an embodiment of the present invention, FIGS. 3 and 4 are operation conceptual diagrams of the device of the present invention, and FIG. 1 is a conceptual diagram of the configuration of a token bus type communication system. N1 to Nn ...... Communication station LN ...... Communication medium 1A, 1B ...... Central processing unit 2A, 2B ...... Communication control device 3A, 3B ...... Active communication control means 4A, 4B ...... Standby communication control means

Claims (1)

[Claims] 1. A plurality of communication stations having a configuration in which a central processing unit and a communication control device are duplicated are connected to each other in a bus shape by a communication medium, and while sequentially exchanging usage rights (tokens) of the communication medium, A communication system for performing communication between communication stations, wherein two communication control devices are connected in each communication station, and a standby communication permission signal line for exchanging standby communication permission signals with each other is provided. When the standby side communication permission command is received from another station in each of the two communication control devices, the standby side communication permission signal is output to the other communication control device side via the signal line, and at the same time, to the own station. When a token is received, there is an active communication control unit that sends the token to the standby communication control device, and a standby communication permission signal that the active communication control device outputs while its own communication control device is on standby. And present And a standby communication control unit that performs a communication operation when a token addressed to the standby side is received from the communication side.