list 	p=16f54 	 
pic54 	    equ 	1ffh 

tmr0b         equ    d'177'


	

tmr0 	equ 	01
pc 	equ 	02
status 	equ 	03
fsr 	equ 	04
ra 	equ 	05
rb 	equ 	06

;-----bit---------------------
z       equ  2 	
c       equ  0
w      equ  0
f      equ  1	
;-----------------------------

  org 000h
main
    movlw  00h
    tris   ra
    movlw  0fh
    movwf  ra
    movlw  d'00000100'
    movwf  option
    movlw  tmr0b
    movwf  tmr0

start

loop    movf   tmr0,w
        btfss  status,z
        goto   loop
        movlw  0fh
        xorwf  ra
        movlw  tmr0b
        movwf  tmr0
        goto   start
;-------------------------------
	org 	0x1ff
 	goto 	main

 	end