Carol,

I've been having a bit of a play with your program, simplifying and rearranging it a bit, and I have it working on a 16F690 (I happened to have one 
handy!).  I've added quite a few BANKSELs just in case - careful investigation could reveal that some of them are removeable.

What it does is turn the LED on at the start, then every 30 seconds it flashes OFF for 1 DELAY time.  I had to change to using Port C as that's where 
the LEDs are on the board I was using.  I've removed the call to DELAY in the Main loop - it doesn't achieve anything.  All the work is done in the ISR, 
which isn't ideal, but it does work!  The potential problem is that calling DELAY in the ISR means that there could be a further interrupt while it's in 
the delay loop, although with the current timing this won't happen.

Oh, and I don't think you were setting the Peripheral Interrupt Enable (PEIE) - this may have been the problem!  :-)

This is what I ended up with:

; ***  PROCESSOR   PIC16F873A
; ***  INCLUDE     P16F873A.inc
   
 PROCESSOR PIC16F690
 INCLUDE     "P16F690.inc"

  errorlevel    -306
  __config    _XT_OSC & _WDT_OFF & _PWRTE_ON

  RADIX       Dec         ; Numbers are Decimal unless otherwise specified
  
  CBLOCK 0x20             ; Declare variable addresses
      LOOP1
      LOOP2
      CONTADOR
      W_TEMP
      STATUS_TEMP
  ENDC

; ================
  ORG     000
          CALL    INIT
          GOTO    MAIN

; ------------------------
; TIMER1 INTERRUPTION
; ------------------------
  ORG 004
          MOVWF   W_TEMP           ; save off current W register contents
          SWAPF   STATUS,W         ; move status register into W register
          CLRF    STATUS              ; select Bank 0
          MOVWF   STATUS_TEMP   ; save off contents of STATUS register

          BANKSEL PIR1
          BTFSS   PIR1,TMR1IF      ; Was it a Timer1 Interrupt?
           GOTO   EXIT             ;  No, skip out

RELOAD                             ;  Yes, process it
          BCF     PIR1, TMR1IF     ; Clear the interrupt indication
          BANKSEL CONTADOR
          DECFSZ  CONTADOR         ; Si el Contador es cero, ya pasaron los 30 segundos
           GOTO   EXIT

          BANKSEL PORTC
          BCF     PORTC,0         ; Turn LED OFF
          CALL    DELAY           ; Wait a bit
          BSF     PORTC,0         ; Turn LED ON
          MOVLW   57              ; Deberia ir un valor de 57
          MOVWF   CONTADOR        ; Reset the counter for 30 secs
EXIT
          MOVF    STATUS_TEMP,W   ; Restore the environment
          MOVWF   STATUS
          SWAPF   W_TEMP,F
          SWAPF   W_TEMP,W
          RETFIE

; ------------------------
; INICIALIZACION
; ------------------------
INIT
          BANKSEL PORTA
          CLRF    PORTA           ; Initialize port A
          CLRF    PORTB           ; Initialize port B
          CLRF    PORTC           ; Initialize port C

          BANKSEL TRISA

          CLRF    TRISA           ; All pins port A output
          CLRF    TRISB           ; All pins port B output
          CLRF    TRISC           ; All pins port C output

          CLRF    PIE1            ; Mask all peripheral interrupts except
          BSF     PIE1,TMR1IE     ;  the timer 1 interrupt
          BANKSEL TMR1L
          CLRF    TMR1L           ; Clear the initial timer count
          CLRF    TMR1H

          BANKSEL PIR1
          CLRF    PIR1            ; Clear peripheral interrupts Flags
          MOVLW   B'00110001'     ; Valor de Prescale = 8, Timer 1 Habilitado
          MOVWF   T1CON
          BSF     INTCON,PEIE     ; Peripheral Interrupt Enable
          BSF     INTCON,GIE      ; Global interrupt enable.

          BANKSEL  CONTADOR
          MOVLW    57             ; Load the Interrupt Counter for 30 seconds
          MOVWF    CONTADOR

; ------------------------
; FUNCTION OF PORT A PINS
; ------------------------
          BANKSEL  ADCON1
          MOVLW    6
          MOVWF    ADCON1         ; All pins digital I/O
          BANKSEL  PORTC
          BSF      PORTC,0        ; Turn on LED connected to RC0
          RETURN

; ----------
; MAIN LOOP
; ----------
MAIN
          GOTO    MAIN

; ---------------
; DELAY 250 mSec
; ---------------
DELAY     MOVLW   250
              MOVWF   LOOP1
OUTER     MOVLW   200
              MOVWF   LOOP2
INNER      NOP
              NOP
              DECFSZ  LOOP2,F
               GOTO   INNER           ; Inner loop = 5 usec.
              DECFSZ  LOOP1,F
               GOTO   OUTER
              RETURN
 END

I hope this is useful!

Cheers,


Howard Winter
St.Albans, England


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