POWER SOURCE VOLTAGE DETECTION CIRCUIT

摘要

PROBLEM TO BE SOLVED: To make the battery exchange of a portable electronic appliance surer. SOLUTION: When the power source voltage drops down to a first voltage, the output of the first detection circuit 1 changes from logical value '0' to logical value '1' and a first flag 3 is set to logical value '1'. Also, when the power source voltage passes the first voltage and lowers down to the second voltage, an output of a second detection circuit 2 changes from the logical value '0' to logical value '1' and a second flag 4 is set at logical value '1'. When a timer circuit 7 outputs an overflow signal OF and an interruption processing circuit 8 generates an interruption request signal, a timer interruption processing is executed, and a microcomputer executes an alarm operation in accordance with conditions of the first flag 3 and the second flag.