PIC18F2480/2580/4480/4580
EXAMPLE 13-1:
RTCinit
MOVLW
MOVWF
CLRF
MOVLW
MOVWF
CLRF
CLRF
MOVLW
MOVWF
BSF
RETURN
RTCisr
BSF
BCF
INCF
MOVLW
CPFSGT
RETURN
CLRF
INCF
MOVLW
CPFSGT
RETURN
CLRF
INCF
MOVLW
CPFSGT
RETURN
MOVLW
MOVWF
RETURN
TMR1H, 7
PIR1, TMR1IF
secs, F
.59
secs
secs
mins, F
.59
mins
mins
hours, F
.23
hours
.01
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?
80h
TMR1H
TMR1L
b’00001111’
T1OSC
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
;
IMPLEMENTING A REAL-TIME CLOCK USING A TIMER1 INTERRUPT SERVICE
; Enable Timer1 interrupt
; No, done
; Reset hours to 1
; Done
TABLE 13-2:
Name
INTCON
PIR1
PIE1
IPR1
TMR1L
TMR1H
T1CON
REGISTERS ASSOCIATED WITH TIMER1 AS A TIMER/COUNTER
Bit 7
Bit 6
Bit 5
TMR0IE
RCIF
RCIE
RCIP
Bit 4
INT0IE
TXIF
TXIE
TXIP
Bit 3
RBIE
SSPIF
SSPIE
SSPIP
Bit 2
TMR0IF
CCP1IF
CCP1IE
CCP1IP
Bit 1
INT0IF
TMR2IF
TMR2IE
TMR2IP
Bit 0
RBIF
TMR1IF
TMR1IE
TMR1IP
Reset
Values
on Page:
TMR1CS
TMR1ON
GIE/GIEH PEIE/GIEL
PSPIF
(1)
PSPIE
(1)
PSPIP
(1)
ADIF
ADIE
ADIP
Timer1 Register Low Byte
TImer1 Register High Byte
RD16
T1RUN
T1CKPS1 T1CKPS0 T1OSCEN T1SYNC
Legend:
— = unimplemented, read as ‘0’. Shaded cells are not used by the Timer1 module.
Note 1:
These bits are unimplemented on PIC18F2X80 devices; always maintain these bits clear.
©
2009 Microchip Technology Inc.
DS39637D-page 159
MICROCHIP [ MICROCHIP TECHNOLOGY ]
