JPS6365258B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a communication control system, and more particularly to a serial communication system configured to send a command signal from a master to a slave and send an acknowledge signal from the slave to the master. This invention relates to an improvement in which command signals and acknowledge signals can be efficiently transmitted and received between a plurality of masters and slaves.

A type of communication control system is configured so that a slave communication control device (hereinafter referred to as slave) returns an acknowledge signal in response to a command signal from a master communication control device (hereinafter referred to as master) to terminate one communication. Some systems are designed to retransmit the same command signal when a communication error occurs to recover from the error.

Specifically, the slave executes a predetermined process such as updating data at a certain address in the database according to the contents of the command signal transmitted from the master, and then transmits an acknowledge signal to the master.

Incidentally, as a form of communication error, a command signal is normally received by a slave and a predetermined process is executed, but an acknowledge signal is not normally transmitted from the slave to the master. In this way, if an error occurs during transmission of an acknowledge signal, the slave will have two
Measures must be taken to prohibit heavy processing.

In order to prohibit such double processing, generally a sequence number is attached to the command signal frame, and it is specified that the slave will not execute consecutive processing with the same sequence number.

However, in such a method, when an m:n system is configured with a plurality of m masters M and a plurality of n slaves S as shown in FIG. In addition to number management, each slave S also manages sequence numbers for each master M.
Special processing at ON/OFF must also be performed.
Control becomes complicated.

As a method to solve these drawbacks, a method has been proposed in which, if an error occurs during acknowledgment signal transmission, the master M sends a command signal to the slave S requesting retransmission of the acknowledge signal frame. If the acknowledgment signal transmitter of the slave S fails, the master M will determine that the first command signal was not received and will retransmit the command signal, resulting in the problem of double processing.

The present invention is designed to avoid such double processing when the transmitting section of the slave S fails, and the slave is provided with means for confirming the transmitting function of an acknowledge signal, and the slave S is provided with means for confirming the transmitting function of an acknowledge signal after receiving a command signal. The present invention is characterized in that the signal transmission function is checked, and if the transmission function is normal, a predetermined process is executed according to the command signal, and an acknowledgment signal is returned after the process is executed.

Hereinafter, it will be explained in detail using the drawings.

FIG. 2 is a block diagram showing a specific example of the slave S constituting the present invention, in which 10 is a receiving section, 2
0 is a transmitting section, and 30 is a logic control section.

The receiving unit 10 includes a receiving circuit 11 that receives a signal from the transmission line L, and a carrier detection circuit 1 that detects that communication is being performed on the transmission line L.
2. It is composed of a reception buffer memory 13 for temporarily storing received signal frames. The transmitting section 20 includes a transmitting buffer memory 21 that temporarily stores an acknowledgment signal frame to be sent back to the master M via the transmission line L, a transmitting circuit 22 that transmits a signal to the transmission line L, and the like. The logic control section 30 controls the operation of each section and controls signal transmission and reception.

The operation of the device configured in this way will be explained.

When a command signal is transmitted from the master M onto the transmission line L, the signal frame is transmitted to the receiving circuit 1.
1 and is temporarily stored in the reception buffer memory 13. The logic control unit 30 is the reception buffer memory 13
The program checks the contents of the address, performs an error check and address check, and if there is an error and the address is not addressed to itself, the signal is ignored, but if there is no error and the address is addressed to itself, it moves to the next step. That is, in the next step, the operational function of the transmitting circuit 22 for transmitting the acknowledge signal is confirmed. In this confirmation, a confirmation signal of a bit pattern that is not recognized as a meaningful signal frame is sent on the transmission line L, this signal is detected by the carrier detection circuit 12, and the detection result is sent to the logic control section 30. Note that, as such a confirmation signal, for example, in a communication system based on the HDLC control procedure, any bit pattern other than the flag pattern can be used. As a result of the confirmation, if carrier detection is not performed, it is determined that the transmitting circuit 22 has failed, and the command signal temporarily stored in the receiving buffer memory 13 is not processed.
On the other hand, as a result of the confirmation, if the transmitting circuit 22 is normal, it executes processing of the received command signal and sends out an acknowledge signal after execution.

According to such a configuration, the transmitting circuit 22 executes processing according to the command signal after confirming the function of transmitting the acknowledge signal to the transmission line L, so that the acknowledge signal is always transmitted to the master M. It turns out. Therefore, if an error occurs in the signal frame due to noise or the like during transmission of the acknowledge signal, there is no need to retransmit the previous command signal from master M, and it is only necessary to request retransmission of the acknowledge signal. In addition, if the acknowledge signal is not returned,
The master M transmits the previous command signal a predetermined number of times, and if there is no response to the predetermined number of transmissions, it is determined that the slave S has failed.

As described above, according to the present invention, it is possible to control the transmission and reception of signals between one or more masters and slaves without using conventional sequence numbers, and this is effective for various communication control systems. It is.

[Brief explanation of drawings]

FIG. 1 is a conceptual diagram of a communication control system according to the present invention, and FIG. 2 is a block diagram showing a specific example of a slave S constituting the present invention. M...Master communication control device (master), S
...Slave communication control device (slave), 10...
...Receiving section, 11...Receiving circuit, 12...Carrier detection circuit, 13...Receiving buffer memory, 20...
...Transmission section, 21... Transmission buffer memory, 22...
...Transmission circuit, 30...Logic control section, L...Transmission line.

Claims (1)

[Claims] 1 Communication using a serial communication method configured such that a command signal is sent from a master to a slave, and the slave performs processing according to the contents of the received command signal and then returns an acknowledge signal to the master. In the control system, the slave includes a receiving circuit that receives a signal from a transmission line, a carrier detection circuit that detects that communication is being performed on the transmission line, and a receiving buffer memory that temporarily stores received signal frames. A receiving section, a transmitting buffer memory that temporarily stores an acknowledgment signal frame to be sent back to the master via a transmission line, a transmitting section including a transmitting circuit that sends a signal to the transmission line, and logic that controls the operation of each section and controls signal transmission and reception. a control unit is provided, and the slave, after receiving the command signal,
The transmitter sends a confirmation signal with a bit pattern that is not recognized as a meaningful signal frame onto the transmission line, and the receiver receives this confirmation signal and checks the transmission function of the acknowledge signal according to the presence or absence of carrier detection. If detection is performed, it is determined that the transmission function is normal, and after executing the specified processing according to the command signal temporarily stored in the reception buffer memory, an acknowledge signal is returned, and if carrier detection is not performed, A communication control system characterized in that the transmission function is determined to be abnormal and the command signal temporarily stored in the reception buffer memory is not processed.