Communication system capable of quickly and impartially arbitrating employment of a data bus

摘要

In a communication system comprising a plurality of interface circuits (11-1 to 11-3) for communicating with a communication device through a data bus (13) and an arbitrator circuit (12) for arbitrating a data bus employment among the interface circuits when the interface circuits communicate with the communication device through the data bus. The arbitrator circuit is connected to the interface circuits by first through third buses (21 to 23). The interface circuits have individual addresses which are different from one another. Each of the interface circuits supplies the first bus with a demand signal which is representative of a level of employing the data bus. The arbitrator circuit supplies a priority address to the second bus in accordance with the demand signal. Each of the interface circuits supplies a conflict address to the first bus in response to the priority address. The arbitrator circuit supplies an arbitration address to the third bus in accordance with the priority address and the conflict address. Each of the interface circuits acquires a transmission right to employ the data bus in accordance with the arbitration address.