User Guide • PC3-ALLEGRO • CompactPCI
®
PlusIO CPU Board • Intel® i7-3xxx Processor
Watchdog
An important reliability feature is a software programmable watchdog function. The PC3-ALLEGRO
contains two of these watchdogs. One is part of the QM77 PCH and also known as TCO Watchdog.
A detailed description is given in the QM77 data sheet. Operating systems like Linux offer a driver
interface to the TCO watchdog.
The behaviour of the 2
nd
watchdog is defined within a PLD of the PC3, which activates/deactivates the
watchdog and controls its time-out period. The time-out delay is adjustable in the steps 2, 10, 50 and
255 seconds. After alerting the WD and programming the time-out value, the related software (e.g.
application program) must trigger the watchdog periodically. For details on programming the
watchdog see section “Board Control and Status Register (BCSR)”.
This watchdog is in a passive state after a system reset. There is no need to trigger it at boot time. The
watchdog is activated on the first trigger request. If the duration between two trigger requests
exceeds the programmed period, the watchdog times out and a full system reset will be generated.
The watchdog remains in the active state until the next system reset. There is no way to disable it once
it has been put on alert, whereas it is possible to reprogram its time-out value at any time.
© EKF -30- ekf.com
