MALFUNCTION PREVENTION CIRCUIT OF MICROPROCESSOR

摘要

PURPOSE:To prevent microporcessor muPC from malfunctioning by applying a reset potential to the reset terminal of muPC more rapidly than a regulated power voltage drops down to the malfunction generating voltage of muPC. CONSTITUTION:The commercial power voltage is rectified 2 via transformer 3, stabilized by voltage stabilizer circuit 4 and applied to power terminal VDD of IC circuit 1 including muPC. When the commercial power supply is cut off momentarily, the potential of terminal VDD of IC circuit 1 drops down to a voltage where muPC may malfunction, but before it, detection circuit 5 composed of Zener diode 52, resistances 53 and 54, and Tr51 detects a drop in the collector potential, unstable potential, of transistor Tr41. This detection voltage holds reset terminal (b) of circuit 1 at a reset potential. Consequently, a digital display unit, etc., controlled by muPC1 can be prevented from malfunctioning in the break of a commercial power supply.