JPS5972844A - Communication control system - Google Patents

Abstract

PURPOSE:To prevent the double processing owing to a fault of a transmission part of a slave station, by testing the function of a transmitter of acknowledge signal after reception of a command signal. CONSTITUTION:A command signal transmitted onto a transmission line L from a master M is stored temporarily in a buffer memory 13 via a receiving circuit 11. A logic control part 30 checks the stored contents of the buffer 13 to perform an error check or an address check. Then a confirmation signal of a bit pattern which is not recognized as a significant signal frame is transmitted onto the line L. This confirmation signal is detected by a carrier detecting circuit 12, and the result of this detection is sent to a logic control part 30. If the absence of carrier is decided, a fault is decided with a transmitting circuit 22 to avoid performing the processing of the received command signal. Then an acknowledge signal is transmitted after the command signal is processed.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a communication control system, and more particularly, to an improvement in a system configured to send a command signal from a master to a slave and return an acknowledge signal from the slave to the master. This system is designed to efficiently transmit and receive command signals and acknowledge signals 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 devices are designed to retransmit a command signal in order to recover from the error when a communication error occurs.

In such a system, if an error occurs in the transmission of the acknowledge signal, a means must be provided to prevent the slave from performing double processing on the retransmitted command signal. .

To prohibit such double processing, a sequence number is generally added 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
In this case, sequence numbers must be managed for each master M, and special processing must also be performed when the power is turned on and off, making the control complex.

As a method to solve these drawbacks, a method has been proposed in which, when an error occurs in acknowledge signal transmission, the master M sends a command signal to the slave 8 requesting retransmission of the acknowledge signal frame. , if the transmitter of the acknowledge signal of the slave S fails, the master M determines that the first command signal was not received and resends the command signal.
This results in the problem of double processing.

The present invention is designed to avoid such double processing when the transmitter of the slave S fails, and the slave is provided with means for checking the transmission function of an acknowledge signal, and after receiving the command signal, the slave S is provided with means for confirming the transmission function of the acknowledge 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 acknowledge 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, 2o is a transmitting section, and 3
0 is a logic control section.

The receiving unit 10 includes a receiving circuit 11 that receives signals from the transmission line L, a carrier detection circuit 12 that detects that communication is being performed on the transmission line L, and a receiving buffer memory 13 that temporarily stores received signal frames. It consists of etc. The transmitting unit 20 includes a transmitting buffer memory 21 that temporarily stores an acknowledge 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. Logic control section 3
0 controls the operation of each part and controls signal transmission and reception.

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

(3) When a command signal is transmitted from the master M onto the transmission line L, the signal frame is temporarily stored in the reception buffer memory 13 via the reception circuit 11.

The logic control unit 30 examines the contents of the reception buffer memory 13, performs an error check and address check, and ignores the signal if there is an error and the address is not addressed to itself, but if there is no error and the address is addressed to itself. In this case, move to the next step. That is, in the next step, the operational function of the transmitting circuit 22 for sending out the acknowledge signal is confirmed. For this confirmation, a confirmation signal with a bit pattern that is not recognized as a meaningful signal frame is sent onto 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 3. Note that such confirmation signals include, for example, HD
In a communication system compliant with LCfltlJN-1@, 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 is malfunctioning, and the received command signal (4) is not processed. On the other hand, if the transmission circuit 22 is normal as a result of the confirmation, 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 connects to the transmission line L.
Since the process is executed according to the command signal after confirming the function of sending an acknowledge signal to the master M, the acknowledge signal is always transmitted to the master M. Therefore, if an error occurs in the signal frame due to noise during transmission of the acknowledge signal, there is no need to retransmit the previous command signal from the master M, and it is only necessary to request retransmission of the acknowledge signal. If the acknowledge signal is not returned, the master M sends out the previous command signal a predetermined number of times, and if there is no response to the predetermined number of sends, 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 sequence numbers as in the past, and it 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, Fig. 2 is a conceptual diagram of a communication control system according to the present invention;
The figure is a block diagram showing a specific example of the slave 8 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... Reception buffer memory, 20... Transmission section, 2
1... Transmission buffer memory, 22... Transmission circuit, 3
0...Logic control unit, L...Transmission line. 7 I En (7)

Claims (1)

[Claims] In a communication control system configured to send a command signal from a master to a slave and return an acknowledge signal from the slave to the master, the slave is provided with means for confirming the sending function of the acknowledge signal, and after receiving the command signal, the acknowledge signal is Check the sending function,
A communication control system characterized in that when a transmission function is normal, a predetermined process is executed according to a command signal, and an acknowledge signal is returned after the process is executed.