Microcomputer

摘要

A microcomputer, in which there is provided a monitoring ROM 100 having a monitoring sense amplifier circuit 113 whose normal operating range for the power supply voltage is set to be narrower than that of the sense amplifier circuit 130 of the ROM 20, and in which the sense amplifier circuit 130 of the ROM 20 is constructed in such a way that it has a plurality of sense amplifier circuit sections and a changeover circuit section, in order to obtain an optimum operating range for a plurality of power supply voltages by changing over the circuit characteristic in accordance with a signal which is supplied by the monitoring ROM 100. The sense amplifier circuit 130 is changed over in order to obtain an optimum operating range for a plurality of power supply voltages, or the frequency of the system clock (E) may be changed over in that a state is detected which is such that the power supply voltage is dropping or the frequency of the system clock E is rising and approaching the operating limit. <IMAGE>