Watchdog circuit for microcomputer programme execution - has synchronising circuit generating square wave input and detector circuit monitoring output during pulse period

摘要

The watchdog circuit includes two stages (10,11) coupled to an input port (8) and an output port (9). One of the stages is a synchronising circuit (10) and the other a detection stage (11). The detection circuit has a coupling stage (R5,C2,R6) for the output signal (Uw). The synchronising circuit provides an input (Us) of a square wave form. The detector circuit checks the level of the output signal level before the input has changed state. If a fault occurs the computer resets. ADVANTAGE - Provides continuous, simple check on programme operation.