Patent ID: 7609714

Claim:
A programmable controller comprising: a CPU unit; a primary communication unit connected to a first network; and a secondary communication unit connected to a second network different from said first network; said primary communication unit being adapted to compile participation status of nodes connected to said first network; said CPU unit being adapted to give priority to said primary communication unit when a request to transmit a communication command is issued to said primary communication unit and said secondary communication unit; said primary communication unit being adapted to judge, when a request to transmit a communication command to an addressee node is received from said CPU unit, whether transmission to said addressee node is possible based on the participation status of said first network, to transmit said communication command if the transmission is judged to be possible and to request said secondary communication unit to transmit said communication command if the transmission is judged to be not possible; said secondary communication unit being adapted to compile participation status of nodes connected to said second network, to judge, when the request for said transmission is received, whether said transmission is possible to said addressee node based on the participation status of said second network, to transmit said communication command if the transmission is possible, to carry out a specified error process if the transmission is mot possible, and to communicate participation status of nodes connected to said second network to said primary communication unit; and said primary communication unit being adapted to select a network to use for the transmission when said request is received, based on the participation status of said first network and the participation status of said second network.