Patent ID: 7515554

Claim:
A half-duplex communication control method in which a first device and a second device are connected by two signal lines and each of the first device and second device notifies the other device of a state related to whether each device is communicable, and half duplex communication in one-to-one correspondence is conducted, said method comprising: the first device outputting a sending request output for providing notification of a state of a communication request from the first device to the second device as a sending request signal using an open collector buffer and also turning back said sending request output inside the first device to check a communicable state inside the first device, and if the second device is receivable with respect to the sending request signal sent from the first device, the second device outputting a sending permission output for providing notification of a communicable state from the second device to the first device as a sending permission signal using an open collector buffer and also turning back said sending permission output inside the second device to check a communicable state inside the second device.