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Philips Semiconductors
Product data
P89C660/P89C662/P89C664/
P89C668
80C51 8-bit Flash microcontroller family
16KB/32KB/64KB ISP/IAP Flash with 512B/1KB/2KB/8KB RAM
2002 Oct 28
60
INIT_WATCHDOG:
MOV CCAPM4, #4CH ; Module 4 in compare mode
MOV CCAP4L, #0FFH ; Write to low byte first
MOV CCAP4H, #0FFH ; Before PCA timer counts up to
; FFFF Hex, these compare values
; must be changed
ORL CMOD, #40H ; Set the WDTE bit to enable the
; watchdog timer without changing
; the other bits in CMOD
;
;********************************************************************
;
; Main program goes here, but CALL WATCHDOG periodically.
;
;********************************************************************
;
WATCHDOG:
CLR EA ; Hold off interrupts
MOV CCAP4L, #00 ; Next compare value is within
MOV CCAP4H, CH ; 255 counts of the current PCA
SETB EA ; timer value
RET
Figure 52. PCA Watchdog Timer Initialization Code