JP2677021B2 - Token bus communication system - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a communication system provided with a plurality of communication control devices connected to a token passing bus for communication.

[0002]

2. Description of the Related Art In the token bus system, of the data on the bus, data to which a special code called a SYNC code is added is treated as a control word. The communication control device connected to the bus transmits based on this control word. Each device connected to the bus has one unique sequence number, and when a token of the control word having the same value as this sequence number appears on the bus, the corresponding device gets the transmission right. If there is data to be transmitted, the device that has acquired the transmission right inserts the data between the control word (BOM) indicating the beginning of the data and the control word (EOM) indicating the end of the data and sends the data to the bus. At this time, a function code (FC) indicating a data receiving destination is added to the BOM, and when the device connected to the bus detects the BOM, it is F
Check C, check if it is the data that should be received, and receive the data.

At the end of transmission or when there is no data to be transmitted, the device having the transmission right sends a token to the bus by adding a value obtained by adding +1 to its own sequence number to pass the transmission right to another device. To do. When the device with the largest sequence number among the devices connected to the bus sends out the token, there is no device with the same sequence number as the sequence number of this token, so
The next token does not appear on the bus. When the token does not appear on the bus within the specified time (time-out), the device with the sequence number 0 gets the transmission right. The sequence number is set at power-on or when a reset instruction is issued.

When each device does not receive a token addressed to itself during one cycle of token circulation, that is, between the timeout and the next timeout, the device decrements its own sequence number by -1. . As a result, when the sequence number has a missing number due to a device failure or the like, the token is normally circulated by closing the missing number. In addition, when a token is newly added during the circulation of the token such as when the power is turned on, it waits for a timeout, and the sequence number of the token at the time of timeout is used as the sequence number of its own device.

[0005]

As described above, the sequence number has a different value depending on the number of devices when the power is turned on and the order of powering on even the same device. Also, when there is a missing number in the sequence number due to equipment failure, etc.,
Each device having a value larger than the sequence number of the device in which the failure has occurred makes the sequence number -1 so that the sequence number is missing so that the sequence numbers are consecutive. Therefore, even if a token sent to the bus is monitored by a bus monitor or the like, it is not possible to know from which device the token was sent. As a result, there is a problem that the evaluation of the device and the failure investigation cannot be performed efficiently.

[0006]

In the token bus communication system of the present invention, tokens and data are transferred to and from each of a plurality of communication control devices connected to the token passing bus. A driver / receiver circuit, a receiver circuit for processing tokens and data received via the driver / receiver circuit, a transmitter circuit for transmitting tokens and data via the driver / receiver circuit, and processing of transmitted / received data And a control circuit for controlling each of the above circuits, and a data processing circuit for executing the above, an ID number storage circuit for storing an ID number to be added to the token, and a control circuit for controlling each circuit. The ID number unique to the device is stored in the ID number storage circuit, and the token is When signal, the ID number added to the ID number stored in the storage circuit, or identifiable to those transmission token transmitted from which of the communication control device.

[0007]

Next, the present invention will be described with reference to the drawings.

Referring to FIG. 1 showing an embodiment of the present invention, a communication control device 1 has a driver / receiver 20 connected to a token passing bus (hereinafter abbreviated as bus) 10. When receiving the initialization message, the driver / receiver 20 sends the initialization message to the reception circuit 21. The reception circuit 21 sends the ID number added to the initial setting message to the ID number storage register 24. Then, the receiving circuit 21 notifies the control circuit 25 that the initial setting message has been received. Upon receiving this notification, the control circuit 25 initializes the communication control device 1 except the ID number storage register 24. When the token is received, the driver / receiver 20 receives the token in the receiving circuit 2
Send to 1. The reception circuit 21 notifies the control circuit 25 that the token has been received and the sequence number added to the token. Upon receiving this notification, the control circuit 25 compares the notified sequence number with the sequence number of its own device, and if they do not match, waits to receive the next token and repeats the above procedure. If they match, it is considered that the own device has acquired the transmission right, and the following process is performed.

First, the control circuit 25 notifies the data processing circuit 23 that the transmission right has been obtained. The data processing circuit 23 that has received the notification sends the data to the transmission circuit 22 when there is data to be transmitted, and the transmission circuit 22 transmits the data to the bus 10 via the driver / receiver 20. When the data has been sent or there is no data to send,
The data processing circuit 23 notifies the control circuit 25 to that effect. Upon receiving this notification, the control circuit 25 notifies the transmission circuit 22 of a sequence number having a value obtained by adding +1 to the sequence number of its own device, and thereafter issues a command to the transmission circuit 22 to transmit the token. The transmission circuit 22 which received this command
When transmitting a token, adds a sequence number of a value obtained by adding +1 to the sequence number of its own device and the ID number stored in the ID number storage register 24 and transmits the token to the bus 10. The above is the processing when the transmission right is obtained.

FIG. 2 shows a token of the communication control device 1. TOK is a code indicating that this communication data is a token. In the conventional device, only the sequence number is added to the token, but in the device of the present invention, the ID number is further added. This ID number is a value unique to each device among the devices connected to the same bus.

FIG. 3 shows a configuration example of the physical bus 10 when communication is performed by the five communication control devices 1 by the token bus method, and before and after communication processing cannot be performed due to a failure of one device. Shows the sequence number of each device and the token change of a specific device. FIG. 3A shows that all five devices are operating, and device 1 with ID number = 6 transmits a token with sequence number = 4 in the figure. FIG. 3B shows an ID number = 3.
3 is an example in which communication processing cannot be performed due to a failure or the like, and the device 1 whose sequence number is larger than 2 in FIG. The setting is shown. And
In FIG. 3B, the device 1 having the ID number = 6 is transmitting the token as in the above. At this time, the sequence number added to the token is 3.

[0012]

As described above, according to the present invention, among the devices connected to the same bus, the ID number unique to each device is stored in the setting circuit and added to the token, so that a bus monitor or the like can be obtained. When you monitor a token sent to the bus, you can see from which device the token was sent. As a result, it is possible to efficiently evaluate the device and investigate the failure.

[Brief description of the drawings]

FIG. 1 is a configuration diagram showing one embodiment of the present invention.

FIG. 2 shows a token of the communication control device in the embodiment.

FIG. 3 is a physical bus configuration example when five devices perform communication by the token bus system in the same embodiment, and each device before and after communication processing cannot be performed due to a failure of one device. The sequence number and the change of the token are shown.

[Explanation of symbols]

 1 Communication Control Device 10 Token Passing Bus 20 Driver / Receiver 21 Reception Circuit 22 Transmission Circuit 23 Data Processing Circuit 24 ID Number Storage Register 25 Control Circuit

Claims (1)

(57) [Claims] 1. A driver / receiver circuit for exchanging tokens and data to and from each of a plurality of communication control devices connected to a token passing system path, and a driver / receiver circuit for exchanging tokens and data. A receiving circuit for processing the received token and data, a transmitting circuit for transmitting the token and data through the driver / receiver circuit, a data processing circuit for processing the transmitted / received data, and an ID added to the token
An ID number storage circuit for storing a number and a control circuit for controlling each circuit are provided, and the ID number peculiar to the device added to the initialization message transmitted at the time of system initialization is stored in the ID number storage circuit. When transmitting a token, the ID number stored in the ID number storage circuit indicates the order of data transmission right, and
With a sequence number that is variably assigned to the device
A token-bus communication system, wherein the token-bus communication system is characterized in that, even when the sequence number is changed, the transmitted token can be identified from which of the communication control units the token was transmitted.