| Field bus technology has been widely used in control system design of industrial manufacturing nowadays. The traditional mode of distributed and computer layered control was gradually substituted by the mode of intelligent terminal and network control. This technology combined the development of process control, automation instrument and computer network technology. According to the existing of multi-bus and difference in the communication protocol, this paper generalized the character of different bus communication protocol and analyzed the data link layer of ISO/OSI mode. Also, the access control mode of bus medium and the compatible design of different protocol were studied in this paper.Aim at the remote control design of the oil supply system, whose communication protocol is difference between the host and target computer, a communication protocol conversion processor based on uPSD3234A single chip computer was presented, it can realized the data exchange freely between host and target computer.The uPSD3234A has two UART serial communication interface, and through the MAX232 chip transfers TTL electrical level to RS232 electrical level, which lead the communication protocol conversion processor has two standard serial interface, one used to connect to the industrial computer with PCAuto software, and another to the CPM2AH PLC which from the OMRON firm.Communication protocol conversion processor has the function of MODBUS slave station and HOST LINK master station, it can communicate with host computer and PLC, which followed MODBUS communication protocol and HOST LINK communication protocol respectively.The information from the PLC such as temperature, pressure, flow and the condition of valve was transmitted to the supervisory software of host computer timely by the Communication protocol conversion processor, and also it can realize remote control of the host computer system. Practically, the design of the communication protocol conversion processor achieved well effectiveness. |
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