The invention discloses a PLC
control system, which comprises a PLC and a plurality of extension modules, wherein the PLC is cascaded with the plurality of extension modules by adopting extension buses; the PLC comprises a
microprocessor and a first extension
bus transceiver, the
microprocessor is used for controlling communication between the PLC and the plurality of extension modules, and the first extension
bus transceiver is used for exchanging data with the first stage extension module through a PLC rear
bus interface; and each extension module comprises an extension
microprocessor and a second extension bus
transceiver, the extension microprocessor is used for controlling communication between the extension module and the PLC, and the second extension bus transceiver is used for exchanging data with the previous stage extension module or the PLC through a corresponding stage front
bus interface and exchanging data with the next stage extension module through a corresponding stage rear
bus interface. The invention further discloses a corresponding PLC extension bus implementation method. Through implementing the technical scheme of the invention, the speed of a PLC extension bus can be increased, the cost is reduced, and the anti-interference capability in the sampling process is high.