PURPOSE: To make it unnecessary to change a set value of a work register, and also to change easily a monitoring time by using a counting value for monitoring a response time, when deciding the response time in an information processing device.

CONSTITUTION: When a start signal from a main body side is received, a count register 11 is cleared to zero, and simultaneously starts a counting operation by + (n) each by synchronizing with a machine clock from the main body. When a stop signal is sent out from a timer 12, a gate 13 becomes a cut-off state, therefore, the count register 11 stops its counting operation. The contents of the count register 11 in this case are read in a counting work register 15 used for monitoring the actual time, some fixed value is subtracted by synchronizing with a machine clock, and the time when the contents of the work register 15 reach zero is set as the upper limit value of the response time. Accordingly, the set value for monitoring the time has no relation to a period of the machine clock.