ADLINK aTCA-6155 - Manual (Page 73)

Watchdog Timer 59
aTCA-6155
7 Watchdog Timer
7.1 Overview
The aTCA-6155 supports a Watchdog Timer function which is built
into the Winbond W83627UHG to protect the system from specific
software or hardware failures that may cause the system stop
responding. The application is first registered with the watchdog
device. Once the watchdog device is enabled, the application
must periodically send a signal to the watchdog device. If the
watchdog device doesn’t receive this signal within the set period of
time, it will reboot the system or restart the application.
The Watchdog Timer of the W83627UHG consists of an 8-bit pro-
grammable time-out counter and a control and status register. The
time-out counter ranges from 1 to 255 minutes in the minutes
mode, or 1 to 255 seconds in the seconds mode. The mode of the
Watchdog Timer counter are selected at Logical Device 8,
CR[F5h], bit[3]. The time-out value is set at Logical Device 8,
CR[F6]. Writing zero disables the Watchdog Timer function. Writ-
ing any non-zero value to this register causes the counter to load
this value into the Watchdog Timer counter and start counting
down.
The W83627UHG outputs a low signal to the WDTO# (pin 77)
when a time-out event occurs. In other words, when the value is
counted down to zero, the timer stops, and the W83627UHG sets
the WDTO# status bit in Logic Device 8, CR[F7h], bit[4], outputting
a low signal to the WDTO# pin (pin 77). Writing a zero will clear
the status bit and the WDTO# pin returns to high. This bit will also
be cleared if LRESET# or PWROK# signal is asserted.