Patent ID: 7912558

Claim:
A PLC for distributed control in a distributed control system together with at least two other PLCs, wherein each of the PLCs is connected to all of the other PLCs to transmit data therebetween, the PLC comprising: a data transmission line connecting said PLC to all of the other PLCs in the distributed control system; a storage unit that stores common-data specifying information for specifying common data shared by respective programs executed by the PLC and the another PLC, wherein the common-data specifying information includes information on an address where the common-data is assigned in a frame of a ladder diagram representing the content of programs to be executed by the PLCs; a receiving unit that receives the common-data specifying information from the another PLC; a collating unit that collates the information on an address stored in the storage unit with the information on an address received by the receiving unit; and a normal data transmission determining unit that determines whether data is normally transmitted between the PLC for distributed control and the another PLC based on the collation of the common-data specifying information stored in the storage unit with the common-data specifying information received by the receiving unit.