Lanner FW-8750 - Manual (Page 39)

FW-8750
39
B. Appendix B: Watchdog Timer
B.1 Introduction
Most systems need to be self-reliant. If an error should occur it is typically
not possible to wait for the system to be rebooted manually. In some cases,
such as apace probes, the system is simply disabled. In other cases, the
speed at which a human operator would reset the system would be too slow
to meet the uptime requirements of the product.
A watchdog timer is a piece of hardware that can be used to automatically
detect system anomalies and reset the processor if the case any problems
are found. Generally speaking, a watchdog timer is based on a counter that
counts down from an initial value to zero. The software selects the counter's
initial value and periodically restarts it. Should the counter reach zero
before the software restarts it, the software is presumed to be
malfunctioning and the processor's reset signal is asserted. Thus, the
processor will be restarted as if a human operator had cycled the power
Note: The watchdog function is from the Intel 82573L. Lanner provides
sample codes and the Intel 82573L datasheet in the Manual/ Driver CD
under the path:// WATCHDOG