PLC system and PLC data transmission method and device

The invention discloses a PLC system and a PLC data transmission method and device, and relates to the technical field of industrial control and the technical field of computers. In the PLC system, an IO scheduler is loaded with configuration information corresponding to an external access unit, and an IO memory area is used for caching data interacted between the IO scheduler and the external access unit; the IO scheduler is used for performing message interaction with the data service module connected with the external access unit according to a preset scheduling strategy based on the configuration information corresponding to the external access unit, so that the data service module exchanges data with the connected external access unit; and the data service module is used for carrying out message interaction with the IO scheduler and carrying out data interaction with the connected external access unit by adopting an industrial protocol supported by the connected external access unit. By adopting the sche