PIC18F1XK22 Datasheet, PDF (106/388 Pages) Microchip Technology – 20-Pin Flash Microcontrollers with nanoWatt XLP Technology

PIC18F1XK22/LF1XK22
EXAMPLE 10-1: 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
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 TMR1 register pair
; for 1 second overflow
; Configure for external clock,
; Asynchronous operation, external oscillator
; Initialize timekeeping registers
;
; Enable Timer1 interrupt
; 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 10-2: 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 RABIE TMR0IF INT0IF RABIF
257
IPR1
—
ADIP
RCIP
TXIP
SSPIP CCP1IP TMR2IP TMR1IP
260
PIE1
—
ADIE
RCIE
TXIE
SSPIE CCP1IE TMR2IE TMR1IE
260
PIR1
—
ADIF
RCIF
TXIF
SSPIF CCP1IF TMR2IF TMR1IF 260
TMR1H Timer1 Register, High Byte
258
TMR1L Timer1 Register, Low Byte
258
TRISA
—
—
TRISA5 TRISA4
—
TRISA2 TRISA1 TRISA0 260
T1CON
RD16 T1RUN T1CKPS1 T1CKPS0 T1OSCEN T1SYNC TMR1CS TMR1ON 258
Legend: — = unimplemented, read as ‘0’. Shaded cells are not used by the Timer1 module.
DS41365D-page 106
Preliminary
 2010 Microchip Technology Inc.