> Van: Jack Raats <jack@JARASOFT.XS4ALL.NL>
> Aan: PICLIST@MITVMA.MIT.EDU
> Onderwerp: help wanted!
> Datum: zondag 25 januari 1998 23:28
>
> I have to write code in which I've to wait minutes. Is it possible to
> use the TIMER0 (TMR0) module to generate such delays?

IF your TIMER0 has an big enough resolution _and_ IF your clock goes slow
enough
it could work ....  :-)

Generaly you mak a setup for the longest wait-time of your TIMER0, and than
create a software-counter on-interrupt (which functions as a extention of
the
hardware-timers).  than let the software-counter set a flag when it
expires.

> If so could anyone send me some source code for example?

The below code is for a PIC16C74, it does not go for the longest
delay-time, but it's only an example ...


;----------------------------

                org Interrupt

;----------------------------
;Because W-register is saved before the Bank-select bits are set for the
Interrupt-routine
;the register-bank in wich the W-register is saved is undetermined.
therefore the Storage-
;register S_WReg exists in _ALL_ register-banks !

                movwf   S_WReg          ;Save W register
                                                ;/ ! S_WReg exists in _ALL_ regi
ster-banks !
                swapf   STATUS,W                ;Save Status register
                bcf     STATUS,RP0              ;/ Select Register-bank #0
                movwf   S_SReg          ;/

                btfsc   PIR1,TMR1IF             ;Call Timer 1 routine
                call    I_Timer                 ;/ on interrupt

                swapf   S_SReg,W                ;Restore Status register
                movwf   STATUS          ;/
                swapf   S_WReg          ;Restore W register
                swapf   S_WReg,W                ;/
                retfie

;----------------------------

;----------------------------
; Initialize Timer #1

InitTimer:      clrf    TMR1L           ;Clear timer #1
                clrf    TMR1H           ;/

                movlw   B'00000001'     ;Initialize Timer #1
                movwf   T1CON           ;/

                bsf     STATUS,RP0      ;Switch to Bank #1
                bsf     PIE1,TMR1IE     ;Enable Timer #1 interrupt
                bcf     STATUS,RP0      ;Switch to Bank #0

                movlw   b'11000000'     ;Enable global & peripheral
                iorwf   INTCON          ;/ interrupts

                return

;----------------------------

I_Timer:                movlw   low  -10000     ;Re-Load timer
                movwf   TMR1L           ;/ (+/- 100 Int's @ a 4MHz crystal)
                movlw   High -10000     ;/
                movwf   TMR1H           ;/

                bcf     PIR1,TMR1IF     ;Clear Interrupt-flag

                decfsz  SoftDelay       ;Return if Software delay not done
                return                  ;/

                movlw   0x??            ;re-Load software counter
                movwf   SoftDelay       ;/

                bsf     DelayDone,0     ;Set flag to indicate that the delay has
 expired

                return

;----------------------------


> With greetings ... Jack Raats

Greetz,
   Rudy Wieser