IMPROVED METHODS AND APPARATUS FOR DISABLING A WATCHDOG FUNCTION

摘要

Apparatus (106) for disabling a watchdog function of a watchdog circuit when an input pin of the circuit (108) fails to receive an externally pulsed signal within a first timeout period. The apparatus (106) includes a pulse generation circuit (401) for generating a pulsed signal with a second timeout period shorter than the watchdog timeout. The apparatus (106) also includes a drive circuit (410) coupled to pulse circuit (401) and watchdog input pin (108). The drive circuit (410) provides an internally pulsed signal to the input pin (108) at a predefined current responsive to the pulsed signal from the pulse circuit (401). The predefined current is sufficient to pull the watchdog input pin (108) to the potential of the internally pulsed signal when the watchdog input pin (108) does not receive the externally pulsed signal. The current level is incapable of pulling the conductor to the potential of the internally pulsed signal when the watchdog input pin (108) receives the externally pulsed signal.