| 摘要 |
<p><P>PROBLEM TO BE SOLVED: To stabilize an output from an I/O port output terminal even on the occurrence of a decrease in a low potential power supply output in a multi power supply microcomputer system using two kinds or more of power supplies. <P>SOLUTION: For example, a CPU 20 is connected between a low potential power supply terminal 11 and a ground potential power supply terminal 13 and a prescribed low potential power supply output (VDDL) is supplied to the CPU 20 via the low potential power supply terminal 11. When a low potential power supply&test mode detection circuit 23 detects a decrease in the low potential power supply output, a level shifter circuit 24 is controlled by a detection output (CLRV) of the circuit 23. Thus, an output level of a peripheral PORT circuit 25 receiving an output from the CPU 20 is controlled to maintain a state before the low potential power supply output is decreased. <P>COPYRIGHT: (C)2007,JPO&INPIT</p> |
