JPS5910102B2 - Loop transmission method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to loop transmission in which a single communication path is arranged in a ring and information circulating in one direction is transmitted in the form of a bit serial. The present invention relates to a loop transmission method that prevents a communication message whose destination station address is unknown from continuing to flow on a loop transmission path.

The present invention will be explained below with reference to the drawings. Figure 1 shows an example of a general loop transmission system, where 1 is a loop transmission line, and A, B, C, and D are loop stations (hereinafter referred to as stations).The role of the station is the loop transmission line 1.
Among the messages sent over the station, only the messages addressed to the station are dropped and transferred to the terminal device connected to the station.

The purpose is to transfer data generated from this terminal device onto the loop transmission line 1. Methods for multiplexing messages on the loop transmission line 1 include a time-division channel multiplexing method in which a time-division unit called a time slot is determined and the message is transferred by placing it in the time slot position, and a time-division channel multiplexing method in which a time-division unit called a time slot is transferred. Although this method is broadly categorized into block multiplexing methods in which messages are placed at appropriate positions and transferred, the above block multiplexing method will be explained here. Now, an example of a case where station A acquires the transmission right by means such as polling and sends a message to station C is as follows.
Station A sends a message in transmission format 2 consisting of the destination station address (in this case, station C), the own station address (in this case, station A), the control code + data + block check character (hereinafter abbreviated as BCC). and place it on the loop transmission path 1 in the direction of loop transfer. Since the destination station address of transmission format 2 is not the station B, station B performs regenerative relay and transfers to the destination. When transmission format 2 arrives, station C first verifies the address of the destination station and its own station, and if the addresses match, it takes in transmission format 2 and checks for message errors with the final BCC. On the other hand, transmission format 2 does not exist on the loop transmission path 1 from station C onward because it has been imported.After importing, station C sends a response confirmation signal to the sending station (station A) in case of an error due to BCC. When the check is correct, the ACK status is prepared, and when the check is incorrect, the NACK status is prepared, a response format 3 is created, and the response format 3 is sent to the loop transmission line 1.

Since station D is unrelated to the communication between station A and station C, reaction format 3
is played back and transmitted to the destination. When response format 3 arrives, station A takes it in and does not send response format 3 on the subsequent loop transmission path 1 o Normally, when response format 3 is ACK, it has been correctly received by the destination station and the transmission is complete. and waives the right to send,
In the case of NACK, transmission format 2 is created again and sent to loop transmission line 1. The general example described above was for a normal situation in which a transmitted message is correctly received at the destination station and a response message is returned. If the destination station address in transmission format 2 changes to an address that does not exist on loop transmission path 1 due to a bit error due to the influence of noise or momentary interruption in the loop transmission system, the transmission at station C The import of format 2 becomes impossible due to an address mismatch, and it is replayed and relayed at the source station A as message 1.4 with an unknown destination station address, causing it to drift around on loop transmission path 1. .

If this message 4 with an unknown destination station address exists on the loop transmission path 1 for a long time, it may cause problems such as collision with the message 4 with an unknown destination station address when the station transfers the message onto the loop transmission path 1. and needed a solution. This invention was made in order to prevent a message 4 with an unknown destination station address from drifting on the loop transmission line 1 for a long time. The reproducing relay operation is stopped between the sending mode and the response receiving mode waiting for a subsequent response.

As a result, even if transmission format 2 changes to destination station address unknown format 4 while being transferred through loop transmission path 1, and becomes unreceivable at any station on 5-loop transmission path 1 and returns to station A again,
Station A has stopped reproducing and relaying, and the destination station address unknown format 4 is discarded here and will not be present on the subsequent loop transmission path 1. FIG. 2 is a block diagram showing an embodiment for explaining the functions of the station described above.

This station has five bodies, each of which is a receiving body 5, a response transmitting body 6, a transmitting body 7, a response receiving body 8,
It is called a relay body 9.

Usually, the signal on the loop transmission line 1 is received by the demodulator 10, stored in the buffer register 12, and input to the modulator 11 via the AND gate 13 and the 0R gate 4. , and is sent to the loop transmission path 1 as a regenerative relay signal. When a transmission request 15 occurs, the configuration is switched to the transmission configuration 7, the transmission data is assembled as in transmission format 2,
The signal is sent from the modulator 11 from the transmission message line 16 via the AND gate 17 and the OR gate 14. After sending,
At the same time as switching the figure to the response receiving figure 8, the timer 18
Start. When the transmission format 2 is received at the destination station and a response is sent back, it is sent to the response status line 20 via the response receiving gate 19. At the same time, the timer 18 is reset. When the transmission format 2 changes during loop transmission to the message 4 with an unknown destination station address, the message returns to the source again, but since it is in the response receiving form 8, no regeneration and relay is performed and the message eventually disappears. The response receiving figure 8 uses a timer 1 set at a time longer than the loop rotation time of the message.
8 timeout time, timeout status line 2
After outputting to 1, it switches to relay figure 9. If the message on the loop transmission line 1 is addressed to the phase station when the relay mode 9 is on, the verification output of the address matching circuit 22 switches the mode to the reception mode 5, and outputs the message to the reception message line 23 via the AND gate 22. . After the reception message ends, the response transmission mode body 6 is switched to receive the response status from the transmission response status line 24, and sent from the modulator 11 via the AND gate 25 and the 0R gate 14. As mentioned above,
After the transmitting station sends a message to the loop transmission path, if the destination station address becomes unknown, the response is sent back to the loop message input section of the transmitting station, taking advantage of the nature of loop transmission in which the message returns to the transmitting station. By stopping the reproducing relay operation until the destination station address is unknown, it is possible to eliminate the problem in which a message whose destination station address is unknown drifts on the loop transmission path for a long time.

[Brief explanation of drawings]

FIG. 1 shows an example of a loop transmission system, and is a diagram for explaining a communication procedure consisting of a transmission message and a response message. FIG. 2 is a configuration diagram for explaining the station function of the present invention. Loop transmission line, 5, 6, 7,
8 and 9 are respectively a receiving body, a response transmitting body, a transmitting body, a response receiving body, and a relay body; 10 is a demodulator; 11 is a modulator;
2 is a buffer register, 18 is a timer, and 22 is an address matching circuit.

Claims (1)

[Claims] 1 In a loop transmission system that includes a destination station address and a local station address in a communication message, and a communication means that confirms a response message from the receiving station after transmitting the communication message between the data sending station and the data receiving station, the communication message A loop transmission system characterized by comprising the above-mentioned data transmitting station which stops regenerative relay operation after completing transmission until reception of a response message, and resumes regenerative relay operation upon arrival of the response message.