Global American 3308520, Руководство пользователя

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3.18 Watchdog Timer
Once the Enable cycle is active a Refresh cycle is requested before the
time-out period. This restarts counting of the WDT period. When the
time counting goes over the period preset of WDT, it will assume that
the program operation is abnormal. A system reset signal will restart
when such error happens.
The following sample programs show how to enable, disable and
refresh the watchdog timer by assembly language:
;----------------------------------------------------------------
;Enter the WDT function mode, interruptible double-write
;----------------------------------------------------------------
MOV
DX, 2EH
MOV AL, 87H
OUT DX, AL
OUT DX, AL
MOV DX, 2EH
MOV AL, 07H
OUT DX, AL
MOV DX, 2FH
MOV AL, 08H
OUT DX, AL
MOV DX, 2EH
MOV AL, F5H
OUT DX, AL ;select CRF0
MOV DX, 2FH
MOV AL, 80H
OUT DX, AL
MOV DX, 2EH
MOV AL, F7H
OUT DX, AL
MOV DX, 2FH
MOV AL, 00H
OUT DX, AL
MOV DX, 2EH
MOV AL, F6H
OUT DX, AL
MOV DX, 2FH
MOV AL, 00H ; *00H=Disabled
OUT DX, AL
;----------------------------------------------------------------
;Exit extended function mode
;----------------------------------------------------------------
MOV DX, 2EH
MOV AL, AAH
OUT DX, AL
User can also use AL, 00H’s defined time for reset purposes, e.g.00H
for Disable, 01H = 1sec, 02H=2sec….FFH=255sec.