Appendix C
Watchdog Timer Programming
©
National Instruments Corporation
C-3
Table C-1.
Watchdog Timer Registers
Address of Register (2E)
Attribute
Description
Read/Write
Value (2F) and description
—
87 (hex)
—
Write this address twice to I/O
address port 2E (hex) to unlock the
W83627HF.
07 (hex)
Write
Write 08 (hex) to select the watchdog
timer register.
30 (hex)
Write
Write 01 (hex) to enable the
watchdog timer function. The default
is disabled.
F5 (hex)
Write
Set seconds or minutes as the timer
unit.
Write 0 to bit 3 (default): second.
Write 1 to bit 3: minute.
F6 (hex)
Write
0: Stop timer
01 to FF (hex) (default): The count
amount, in seconds or minutes,
depends on the value set in register
F5 (hex). This number determines
how long the watchdog timer waits
for the strobe before generating an
interrupt or reset signal. Writing a
new value to this register resets the
timer to count with the new value.
F7 (hex)
Read/Write
Bit 6: Write 1 to enable the keyboard
to reset the timer. Write 0 to disable.
Bit 5 (default): Write 1 to generate a
timeout signal immediately and
automatically return to 0.
Bit 4 (default = 0): Read the
watchdog timer status. 1 means the
timer is timeout.
AA (hex)
—
Write this address to I/O port 2E
(hex) to lock the watchdog timer.
