strange behavior in MPASM simulator using timer interrupt (PIC16F84)

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I'm using the timer interrupt of the PIC16F84 to make a very long time delay and I'm running it in the simulator of MPASM. I have a spin loop that when I set a breakpoint in it, it never arrives there when I set a breakpoint in the interrupt. I'm wondering if for some reason the simulator just ignores the main loop when breaking in the interrupt. Here's the code:

list      p=16F84            ; list directive to define processor
	#include  <P16F84.inc>        ; processor specific variable definitions

	__CONFIG   _CP_OFF & _WDT_OFF & _PWRTE_OFF & _RC_OSC

; '__CONFIG' directive is used to embed configuration data within .asm file.
; The lables following the directive are located in the respective .inc file.
; See respective data sheet for additional information on configuration word.


;***** VARIABLE DEFINITIONS
w_temp				EQU     	0x0C        ; variable used for context saving 
status_temp			EQU     	0x0D        ; variable used for context saving

		CBLOCK	0x0E
			mode					; bit 0 set = wait - clear = OK
									; bit 1 button state 0 = off - 1 = on
									; bit 2 reset mode 1 = yes - 0 = no
			valve_on_time
			CounterA
			CounterB
			CounterC
			CounterD
			CounterE
			temp1
		ENDC

;**********************************************************************
		ORG     0x000             ; processor reset vector
  		goto    main              ; go to beginning of program


		ORG     0x004             ; interrupt vector location
		goto	interrupt

main
		bcf		INTCON,GIE
		bcf		INTCON,T0IE
		bsf		STATUS,RP0
		bcf		OPTION_REG,T0CS		; set timer to timer mode
		bcf		OPTION_REG,PSA		; select prescaler
		bsf		OPTION_REG,PS0		; set prescaler to max value
		bsf		OPTION_REG,PS1
		bsf		OPTION_REG,PS2

		movlw	D'255'
		movwf	CounterB
		movlw	D'255'
		movwf	CounterA
		movlw	0
		movwf	mode
		call		set_interrupt

spin:	
		clrwdt
;		movlw	3
;		subwf	mode,W
;		btfsc	STATUS,Z
;		goto	out
;		goto	spin
		
out:
		nop
		goto	out		
		
;**********************************************************************
set_interrupt:
		bsf		INTCON,GIE
		bsf		INTCON,T0IE
		return

;**********************************************************************
interrupt
		movwf		w_temp			; save off current W register contents
		movf		STATUS,w		; move status register into W register
		movwf		status_temp		; save off contents of STATUS register

		bcf			INTCON,T0IF		; clear interrupt flag for timer
		clrwdt
		
		decfsz	CounterA,1
		goto	exit_interrupt
		decfsz	CounterB,1
		goto	exit_interrupt
;		bsf		mode,0		
		incf		mode      ; setting breakpoint here
		movlw	D'255'
		movwf	CounterB
		movlw	D'255'
		movwf	CounterA
		
exit_interrupt:
		bsf			INTCON,T0IF
		movf		status_temp,w	; retrieve copy of STATUS register
		movwf		STATUS			; restore pre-isr STATUS register contents
		swapf		w_temp,f
		swapf		w_temp,w		; restore pre-isr W register contents
		retfie						; return from interrupt