Appendix A Programming the Watchdog Timer 55
Table A-1: Watchdog timer registers
Address of
register (2E) Attribute Description
Read/Write Value (2F)
and
description
87 (hex) ----- Write this address to I/O address
port 2E (hex) twice to unlock the
W83627HF
07 (hex) write Write 08 (hex) to select register of
watchdog timer.
30 (hex) write Write 01 (hex) to enable the function of
the watchdog timer. Disabled is set as
default.
F5 (hex) write Set seconds or minutes as units for
the timer.
Write 0 to bit 3: set second as counting unit. [default]
Write 1 to bit 3: set minute as counting unit
F6 (hex) write 0: stop timer [default]01~FF (hex): The
amount of the count, in seconds or
minutes, depends on the value set in
register F5 (hex). This number
decides how long the watchdog timer
waits for strobe before generating an
interrupt or reset signal. Writing a new
value to this register can reset the
timer to count with the new value.
F7 (hex) rd/wr Bit 6: Write 1 to enable keyboard to
reset the timer, 0 to disable.[default]
Bit 5: Write 1 to generate a timeout
signal immediately and automatically
return to 0. [default=0] Bit 4: Read
status of watchdog timer, 1 means
timer is "time out".
AA (hex) ----- Write this address to I/O port 2E (hex)
to lock the watchdog timer.2