PIC18F87J90 Datasheet, PDF (147/450 Pages) Microchip Technology – 64/80-Pin, High-Performance Microcontrollers with LCD Driver and nanoWatt Technology

PIC18F87J90 FAMILY
EXAMPLE 12-1: IMPLEMENTING A REAL-TIME CLOCK USING A TIMER1 INTERRUPT SERVICE
RTCinit
RTCisr
MOVLW
MOVWF
CLRF
MOVLW
MOVWF
CLRF
CLRF
MOVLW
MOVWF
BSF
RETURN
80h
TMR1H
TMR1L
b’00001111’
T1CON
secs
mins
.12
hours
PIE1, TMR1IE
; Preload TMR1 register pair
; for 1 second overflow
; Configure for external clock,
; Asynchronous operation, external oscillator
; Initialize timekeeping registers
;
; Enable Timer1 interrupt
BSF
BCF
INCF
MOVLW
CPFSGT
RETURN
CLRF
INCF
MOVLW
CPFSGT
RETURN
CLRF
INCF
MOVLW
CPFSGT
RETURN
CLRF
RETURN
TMR1H, 7
PIR1, TMR1IF
secs, F
.59
secs
secs
mins, F
.59
mins
mins
hours, F
.23
hours
hours
; Preload for 1 sec overflow
; Clear interrupt flag
; Increment seconds
; 60 seconds elapsed?
; No, done
; Clear seconds
; Increment minutes
; 60 minutes elapsed?
; No, done
; clear minutes
; Increment hours
; 24 hours elapsed?
; No, done
; Reset hours
; Done
TABLE 12-2: REGISTERS ASSOCIATED WITH TIMER1 AS A TIMER/COUNTER
Name
Bit 7
Bit 6
Bit 5
Bit 4
Bit 3
Bit 2
Bit 1
Bit 0
Reset
Values
on page
INTCON GIE/GIEH PEIE/GIEL TMR0IE INT0IE
RBIE TMR0IF INT0IF
RBIF
59
PIR1
—
ADIF
RC1IF TX1IF SSPIF
—
TMR2IF TMR1IF
62
PIE1
—
ADIE
RC1IE TX1IE SSPIE
—
TMR2IE TMR1IE
62
IPR1
—
ADIP
RC1IP TX1IP SSPIP
—
TMR2IP TMR1IP
62
TMR1L Timer1 Register Low Byte
60
TMR1H Timer1 Register High Byte
60
T1CON
RD16 T1RUN T1CKPS1 T1CKPS0 T1OSCEN T1SYNC TMR1CS TMR1ON 60
Legend: Shaded cells are not used by the Timer1 module.
 2010 Microchip Technology Inc.
DS39933D-page 147