EKF PC7-FESTIVAL, User Manual

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User Guide • PC7-FESTIVAL • CompactPCI® PlusIO CPU Board
Watchdog
An important reliability feature is a software programmable watchdog function. The
PC7-FESTIVAL contains two of these watchdogs. One is part of the CM238 PCH and also known as
TCO Watchdog. A detailed description is given in the CM238 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 PC7-FESTIVAL, 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 programming the time-out value and
arming the WD, 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.
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