There are two registers involved with the Software Watchdog (see the SIM book, pages 3-7 through 3-9 and pages 3-12 through 3-13)
- SYPCR - System Protection Control Register
On power up, we write 0xc0 to this register. This sets the Software Watchdog Enable bit, SWE. This also enables the clock Prescaler by 512, SWP and SWT bits. The ratio selected, 2^18 is divided by the external system crystal frequency,
32768, to obtain the watchdog timeout in seconds, 8.I have fiddled around with the HME, BME, and BMT bits, but it made no difference.
- SWSR - Software Service Register
This register is written to about every sixth of a second in a task. If this register is not written to, the watchdog times out and asserts the reset signal.
Perform a watchdog service as follows:
Write 0x55 to the SWSR Write 0xAA to the SWSR
PROBLEM: When I disable the task that services the watchdog, I expect in 8 seconds for the system to reset. In 8 seconds, I hear the fans shut off, but the actual reset does not take place. It varies to when it does.. Anywhere from several seconds to several minutes afterwards.
Any ideas??