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A.2 Watchdog Timer Programming
The I/O port address of the watchdog timer is 2E(hex) and 2F(hex), 2E
(hex) is the address port. 2F(hex) is the data port. You must first assign
the address of register by writing address value into address port 2E(hex),
then write/read data to/from the assigned register through data port 2F
(hex).
Table A.1: Watchdog Runtime Registers
Name
WDT_TIME_
OUT
WDT_VAL
WDT_CFG
WDT_CTRL
REG
OFFSET
(HEX)
65
66
67
68
DESCRIPTION
Watch-dog Timeout
Bits[6:0] Reserved
Bit[7] WDT Time-out Value Units Select
= 0 Minutes
= 1 Seconds
Watch-dog Timer Time-out Value
Binary coded, units = minutes or sec-
onds, selectable via Bit[7] of
WDT_TIME_OUT register (0x65).
0x00 Time out disabled
0x01 Time-out = 1 minute (second)
.....
0xFF Time-out = 255 minutes (seconds)
Bit[0] Reserved
Bit[1] Keyboard Enable
=1 WDT is reset upon a Keyboard inter-
rupt.
=0 WDT is not affected by Keyboard
interrupts.
Bit[2] Mouse Enable
=1 WDT is reset upon a Mouse inter-
rupt.
=0 WDT is not affected by Mouse inter-
rupts.
Bit[7:3] Reserved
Bit[1] Reserved
Bit[2] Force Timeout,
=1 Forces WD timeout event; this bit is
self-clearing
Bit[7:3] Reserved
27
Chapter A
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