PURPOSE: To increase the number of I/O loads which can be connected to one output port by making its output port combine in use a dynamic scan pulse output to an input port and a direct output to a load.

CONSTITUTION: Both a pulse detecting circuit 6 and switching circuits 5aW5d are connected to an output port O2, and at the time of detecting a switch input, output ports O0WO2 are in a dynamic scan state, output voltage generates a repeated pulse of a prescribed period, and an indicator 7 is not lighted. On the other hand, when a microcomputer 1 halts a scan by a prescribed condition, the output voltage of the port O2 becomes a low level, the indicator 7 is lighted, and it is informed that the dynamic scan is stopped. Also, a dynamic scan pulse output to an input port and a direct output to a load can be combined in use to other output ports O0, O1, respectively, as well.