JPS58177051A - Communication device - Google Patents

Abstract

PURPOSE:To use the communication line efficiently, by occupying a communication circuit for the communication, only when a request of data transmission is generated. CONSTITUTION:A data signal transmitted from other communication devices is inputted to a reception circuit 2 via a bus BUS and an MODEM circuit 1 and a monitor circuit 4. The circuit 4 monitors the reception of a command at all times and monitors whether or not a status change representing the status change of a process state takes place in a data inputted from a data generating source via an internal bus 4a. If any status change is generated in the data, the communication device takes over the right of communication, transmits the response to other communication devices via a transmission circuit 3, the circuit 1 and the BUS and starts a frame producing circuit 5. The circuit 5 produces the address and command of the communication device to which data transmission is designated, they are added to a data signal transmitted by the circuit 4, and transmitted to the BUS via the circuits 3 and 1.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a communication device that shares a communication line and transmits and receives data in a time-division manner.

Conventionally, in this type of communication device, when one communication device cyclically transmits status information of process equipment from many other communication devices, the transmission is performed at a predetermined period even if the status information does not actually change. The receiving side was required to send a response each time it was received. This type of communication has poor communication efficiency and requires a long time to transmit the same amount of information when the communication speed is constant, compared to one that only communicates when there is a change in the situation. On the other hand, if the communication time is fixed, high-speed communication must be used to transmit the same amount of information, which is technically and economically disadvantageous.

This invention was made in order to eliminate the drawbacks of the conventional system, and it transmits data only when it is necessary to transmit the data, and remains in the receiving state during the rest of the time, thereby reducing the communication line. - It is an object of the present invention to provide a communication device that enables effective use of.

An embodiment of the present invention will be described below with reference to the drawings. 1st
The figure shows that communication devices CMI to CMn according to the present invention are connected to bus B.
It is a diagram showing that they are mutually connected by US.

Each of the communication devices CMI to CMn has a configuration as shown in FIG. 2. In FIG. 2, 1 is a modem circuit, 2 is a receiving circuit, 3 is a transmitting circuit, 4 is a monitoring circuit, and 5 is a frame generating circuit.

Data signals sent from other communication devices are transferred to the bus BUS.
and is input to the receiving circuit 2 via the modem circuit 1, where it is converted from a serial format signal to a parallel format signal, and then
The signal is input to the monitoring circuit 4.

The monitoring circuit 4 constantly monitors the reception of a data signal, that is, a command indicating the transfer of communication rights that enables the communication device to send a data signal from the signal from the receiving circuit 2, and sends a data signal via an internal bus 4a, as shown in the figure. It is monitored whether or not a change in state indicating the state of the process has occurred in the data manually inputted from the process equipment or data source. If a change in status occurs in the data, the relevant communication device receives this status change as a data transmission request and receives a communication right, and sends a data signal, that is, a response indicating acquisition of the communication right, to the transmitting circuit 3.
The frame generation circuit 5 is then sent to other communication devices via the modem circuit 1 and the bus BUS, and the frame generation circuit 5 is activated. Then, the frame generation circuit 5 generates the destination address of the communication device to which the data signal indicating the occurrence of the status change is sent and a command requesting reading of the data signal, and adds these to the data signal sent out by the monitoring circuit 5. , i.e. generate a frame,
It is sent to the bus BUS via the transmitting circuit 3 and modem circuit 1.

As described above, according to the present invention, only when a change in status occurs, that is, only when a request to send data occurs,
Since communication is carried out by occupying a communication line, one communication line can be used efficiently, and many pieces of data from many communication devices can be communicated in a short time without increasing the communication speed. It has a calming effect.

[Brief explanation of the drawing]

FIG. 1 is a connection diagram showing connections between communication devices according to the present invention, and FIG. 2 is a block diagram of a four-way device according to an embodiment of the present invention. CMI to CMn...communication device, 1...modem circuit,
2... Receiving circuit, 3... Transmitting circuit, 4... Monitoring circuit, 5... Framing JilJM.

Claims (1)

[Claims] In a communication device that is connected to each other via a common communication circuit and to a unique data generation source, the data generation source transmits data inputted from the data generation source to the communication line. a monitoring circuit that monitors whether or not there is a request to send data, and outputs a signal to set the communication device in question to a sending state when this request is detected; and a monitoring circuit that responds to the signal. and a frame generation circuit that generates a destination address for the data and sends it to a communication line.