Interrupt input circuit

摘要

PURPOSE:To improve the using efficiency of a microcomputer by adding a circuit which produces an interruption request signal in response to an external signal in a stand-by state. CONSTITUTION:An interruption input circuit 21 delivers an interruption request signal in response to the signal given from outside in a stand-by state where the system clock is stopped. Then the request signal is applied to an interruption control circuit 22. Then circuit 22 gives the request signal to a CPU23. Thus a clock circuit 25 is actuated via a start circuit 24 as long as the CPU23 is set in an interruption allowable state. Then the system clocks are applied to the CPU23, the circuit 21 and a peripheral circuit 26 from the circuit 25. Then the CPU23 executes the interruption processing.