Datasheet

Philips Semiconductors Product specification
8XC54/58
8XC51FA/FB/FC/80C51FA
8XC51RA+/RB+/RC+/RD+/80C51RA+
80C51 8-bit microcontroller family
8K–64K/256–1K OTP/ROM/ROMless, low voltage (2.7V–5.5V),
low power, high speed (33MHz)
2000 Aug 07
32
(8XC51FX and 8XC51RX+ ONLY)
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 26. PCA Watchdog Timer Initialization Code