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AIMB-221 User Manual 92
A.3.1 Example Programs
Enable watchdog timer and set 10 seconds as the timeout interval
;-----------------------------------------------------------
Mov dx,2eh ; Unlock W83627HF
Mov al,87h
Out dx,al
Out dx,al
;-----------------------------------------------------------
Mov al,07h ; Select registers of watchdog timer
Out dx,al
Inc dx
Mov al,08h
Out dx,al
;-----------------------------------------------------------
Dec dx ; Enable the function of watchdog timer
Mov al,30h
Out dx,al
Inc dx
Mov al,01h
Out dx,al
;-----------------------------------------------------------
Table A.1: Watchdog timer registers
Address of
register (2E)
Read/Write Value (2F) & 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 seconds as counting unit. [default]. Write 1 to bit
3: set minutes 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) read/write 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
"timeout".
AA (hex) ----- Write this address to I/O port 2E (hex) to lock the watch-
dog timer 2.