Watchdog Circuitry - Matrox Morphis QxT Installation And Hardware Reference

Watchdog circuitry

Matrox Morphis QxT integrates Watchdog circuitry to automatically recover from
application or system failure. The Watchdog circuitry automatically reboots your
computer when, for some reason, your computer hangs for longer than a pre-set
amount of time.
The Watchdog circuitry works based on several integrated timers. When the
Watchdog circuitry is enabled, it must receive a reset signal from the user
application within the time specified by a timer. Every time the signal is received,
the Watchdog circuitry resets this timer. If, however, the Watchdog circuitry does
not receive a reset signal for a period longer than the time allotted by this timer,
it will either send a warning interrupt signal or a hardware signal to reboot the
computer, depending on the timer.
There are three main timers that make up the Watchdog circuitry:
• Warning timer. If, during the course of regular operations, the Host computer
does not reset the warning timer before the specified interval expires, it is assumed
to have hung. The Watchdog's warning timer will then generate a warning
interrupt.
• Timeout timer. If, during the course of regular operation, the Host computer does
not reset the timeout timer before the specified interval expires, it is assumed to
have hung. The Watchdog's timeout timer will then force the Host computer to
reboot.
• Reboot timer. If, during a reboot, the Host computer does not start regular
operations before the specified interval expires, the Host computer is assumed to
have hung. The Watchdog's reboot timer will then force the Host computer to
reboot again.
You can enable the Watchdog circuitry and set and reset the Watchdog timers
using the MIL-Lite MsysControl() function. You can hook an event handler
function to the warning interrupt using MsysHookFunction().
Watchdog circuitry 39