Читать книгу Design for Excellence in Electronics Manufacturing - Cheryl Tulkoff - Страница 30

This procedure is intended to verify that that the systems supervisor circuit was correctly implemented and is effective at recognizing faults and initiating corrective action attempts. Digital microprocessing devices use a “dead man's switch”‐like supervision circuit (a.k.a. watchdog or COP (computer operating properly) to monitor for the continued presence of a state of health (SOH) indicator signal. To ensure that disruptions and faults can be rapidly detected and corrected, the supervisor circuit monitors pulses the microprocessor is programmed to send within specified time intervals as the result of handshaking typically between timing interrupt routines and the main programming loop. If the supervisor is not toggled in time, it is assumed that the processor is hung up or executing an endless loop. The supervisor then generates a pulse to the processor to warn that a fault has occurred; typically, this directly or indirectly triggers a system reset that also triggers a diagnostics counter that documents the number of COP‐triggered resets over a specified number of system power‐up activation cycles.