| 摘要 |
PURPOSE:To guarantee the right of using the common bus of a host bus master, by providing a timer means which outputs a second bus use request signal to the host bus master for a prescribed time as a bus use request signal based on a first bus use request signal. CONSTITUTION:When the bus use request signal HOLD from a slave bus master 2 is continued to be outputted, a timer 4 recognizes it as the fault of the slave bus master 2, and at a time t2, that is, after the lapse of a timer time T1 from a time t1, interrupts a bus use second-order request signal HRQ to the host bus master 1. Therefore, simultaneously, since the host bus master 1 interrupts a bus use permission signal HLDA for the slave bus master 2, the slave bus master 2 stops the use of a common bus CB. And the host bus master 1 can start the use of the common bus CB again. In such a way, it is possible to guarantee the right of using the common bus CB of the host bus master 1. |
