Watchdog. EKF PC3-ALLEGRO

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