Communication system between PLC and module and implementation method

The invention relates to the technical field of PLC control, in particular to a communication system between a PLC and a module, which comprises a PLC and an extension module, and is characterized in that the PLC comprises an MPU module and a main FPGA module which are connected with each other; the extension module comprises an MCU module and a slave FPGA module which are connected with each other; the PLC is connected with the expansion module through a connector module; the connector module comprises a connector male head and a connector female head which can be plugged with each other; the master FPGA module is connected with a connector female head. The slave FPGA module is connected with a connector male head. According to the system and the method, the number of downlink data links and the number of uplink data links for communication between the PLC and the extension module are respectively two, when one of the downlink data links or the uplink data links has an error, the other data link can be switc