Patent ID: 8203361

Claim:
A circuit system comprising: a first circuit sub-system, a second circuit sub-system, and a bidirectional bus coupling the first circuit sub-system and second circuit sub-system, the first circuit sub-system comprising; a first control circuit that receives a control signal for controlling the direction of the bidirectional bus, and controls the first sub-system to be either of a transmitting state or a receiving state based on a state of the control signal; a first sending unit that receives the control signal, and outputs as a first control signal; and a second sending unit that receives the control signal, and outputs as a second control signal; the second circuit sub-system comprising; a first receiving unit that receives the first control signal from the first sending unit; a second receiving unit that receives the second control signal from the second sending unit; and a second control circuit that controls the second sub-system to assume either the transmitting state or the receiving state in accordance with the state of the first control signal received by the first receiving unit and the second control signal received by the second receiving unit when the first and second control signals indicate the same state, and controls the second sub-system to assume the receiving state when the first and second control signals indicate different states from each other.