Watchdog timer device for microcomputer system

摘要

PURPOSE:To provide a watch dog timer device for a LAN microcomputer system, etc., for car free from risk of the battery being exhausting, by lessening the current consumption in the system during the sleep. CONSTITUTION:The power supplied from a power supply circuit 3 of a microcomputer system is divided into a VccI power line 7, which is held turned on even during the sleep, and a VccII power line 8 to be turned off during the sleep by a VccII on/off circuit 6, and also a watch dog timer 2 is furnished independent from the microcomputer 1, and the power supply of this watch dog timer 2 is connected with the VccII power line 8. When the microcomputer system is put in sleep state, the power supply of the watch dog timer 2 is turned off automatically, which should reduce the current consumption during the sleep and also eliminates any pseudo P.RUN signal generator circuit for preventing misdiagnostic motions of the watch dog timer 2 when the system is in sleep. Thus the current consumption can be reduced accordingly.