See the top level README for information on where to find the
schematic and programmers reference manual for the ARM processor
on the raspberry pi.  Also find information on how to load and run
these programs.

So when surfing through the linux source for the raspberry pi I found
some watchdog timer registers that dont appear to be in the datasheet.

So I played with the registers a bit and it appears that from reset
and/or using the settings as configured in this code, the watchdog
timer is a divide by 4000 of the system timer, so 250,000,000/4000 =
62500 Hz.

Based on assumptions from the linux code the biggest timer is 0xFFFFF
which is 16.8 seconds.  If you do not reprogram the timer and let it
run out, then it resets the chip, down to re-reading the sd card and
bringing the ARM up using kernel.img.

This example simply uses the watchdog timer to time the led state
changes.  Because it reprograms the watchdog timer with a new time
the timer does not timeout and reset the chip.  Comment out or remove
the break in the loop and it will timeout and reset the chip.