| 摘要 |
PURPOSE:To decrease the number of ports down to half and to realize a compact package, by transferring an external interruption factor to a CPU by a pseudo bidirectional port and at the same time resetting the external interruption factor through the same port. CONSTITUTION:The signals of external interruption factors I0 and I1 are applied to each clock pulse CP terminal of flip-flops 40 and 41. Thus an external interruption signal INT is produced to be applied to a CPU1. The CPU1 accepts an external interruption with an interruption input signal INT and then reads the levels of output terminals A0 and A1 of switching circuits 50 and 51 through two pseudo bilateral ports 2 and 3. The CPU1 performs an external interruption process in terms of software and switches the ports 2 and 3 to an output mode. Thus both ports 2 and 3 deliver ''0''. As a result, both flip-flops 40 and 41 are perfectly reset, and the CPU1 prepares for acceptance of the next interruption signal. |
