S7-200的发送、接收程序，可以和PIC单片机通信，通过通信口控制PLC触点-the code of transmiting or receiving UART signal in S7-200 PLC, which can be connected to PIC or other MCU, and by which ,PIC can control the ON or OFF status of PLC output

51单片机和s7-200自由口的MODBUS通信的单片机MODBUS从站程序-51 free chip and s7-200 MODBUS communication port of the microcontroller program MODBUS slave