RS-485 serial port pseudo-full-duplex communication research and application

The RS-485 serial port communication is very popular in a monitoring and controlling system. A concept of RS-485 free port pseudo-full-duplex communication is presented in this paper, that is, RS-485 can not only send timed messages continuously but also receive messages at any moment from the host computer. Since RS-485 serial port has the advantage of far distance communication and anti-jamming, if it can be used as full-duplex communication mode, it will be very popular in industry fields. It was realized by upper computer or lower computer in this paper. Experiments and field tests show that this program can work reliably. Now it has been used successfully in the part of ground equipments in the field of aerospace engineering, in the system of remote control and monitoring. Hence, for the remote control computer, most of the time, it just deals with receiving messages from the PLC S7-200, that saves the computer CPU resources. It is very convenient for the equipment debugging people, for that he even can only use any kind of serial debugging software to receive data from the PLC S7-200, and he will know the status of the equipment, need not program a complicated host computer software temporarily himself.