Watchdog Timer - VersaLogic EPM-4 Reference Manual

Watchdog Timer

There is a flexible watchdog timer integrated into the ÉlanSC520 Microcontroller. It supports a
time-out period up to 30 seconds, and can generate an interrupt, NMI, or system reset when time-
out occurs. The watchdog registers are protected by write key sequences.
See the following pseudo code as a simple example of watchdog operation.
MMCR_base = DF00:0h
WDTMRCTL
MemWrite WDTMRCTL, 03333h
MemWrite WDTMRCTL, 0CCCCh
MemWrite WDTMRCTL, 0C010h
Begin program loop
MemWrite WDTMRCTL, 0AAAAh
MemWrite WDTMRCTL, 05555h
End program loop
For detailed programming instructions for the integrated watchdog timer, see chapter 19 of the
ÉlanSC520 Microcontroller User's Manual, and chapter 16 of the Register Set Manual.
EPM-4 Reference Manual
; segment:offset address
= MMCR_base + 0CB0h
; Key sequence to allow write access to
; control
; register. These are 16-bit memory writes.
; Enable watchdog timer. 4 second timer.
; Reset on timeout.
; perform useful instructions here that
; will never take more than 4
; seconds to complete.
; Key sequence to reset the timer
; countdown
; These are 16-bit memory writes.
Watchdog Timer
Reference – 33