Visual Basic based serial communication between PLC S7200 and host computer and its application

While PLC serves as slave computer to realize data collection function,data communication between PLC and host computer is a key link.It is necessary to investigate serial communication mechanism between PLC and host computer.Through analyzing the serial communication principle and approach of SIEMENS SIMATIC S7-200 PLC and host computer,the program design method for communication between PLC and host computer was given based on Visual Basic.The designed program ensures the communication between S7-200 PLC and host computer,and has been used for designing an automatic unloading tyre manipulator.The scheme has realistic meaning for small scale control systems.