Can anyone advise me on what I'm missing in getting interrupts to work =
using the timer1 overflow on the 16F876.
I have to admit to never having used interrupts before, so it may be =
obvious to those who have.....

My code includes the following:

  ORG     0x000             ; processor reset vector
    goto    main              ; go to beginning of program
  ORG     0x004             ; interrupt vector location

  bank_low
  CLRWDT
  btfss PIR1,TMR1IF ;return if it wasn't a timer1 interrupt
  retfie
  movlw h'dc'
  movwf TMR1L  ;set timer1 to BDC, i.e. 3036 to give .5sec interval =
including prescaler
  movlw h'0b'
  movwf TMR1H
  call letters
  ;rest of handler here

  bcf PIR1,TMR1IF
  retfie

;end of interrupt routine
;**********************************************************************
main =20
;
;other code here
  movlw b'00110000' ;set prescaler to 1:8
  movwf T1CON
  movlw h'dc'
  movwf TMR1L  ;set timer1 to BDC, i.e. 3036 to give .5sec interval =
including prescaler
  movlw h'0b'
  movwf TMR1H
  bcf PIR1,TMR1IF ;ensure interrupt flag is clear
  movlw b'11000000' ;global interrupts, peripheral only
  movwf INTCON
  movlw b'00000001' ;Timer1 only
  movwf PIE1

  bsf T1CON,TMR1ON ;enable timer1

  call initdisplay

I know the timer 1 overflow flag gets set, but never calls the interrupt =
vector.

Any help greatly appreciated.

Malcolm.

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