> start:          btfss   PORTA,1                 ;is RA.1 high?
        ;OP said LED must go on when A.1 grounded, so should be:
start:          btfsc   PORTA,1         ;is RA.1 low

                goto    sw_off                  ;no
                ;label changed for clarity

sw_on                movlw   04h                     ;yes
                ;label added for clarity
>                movwf   PORTA                   ;turn LED on
>                goto    start                   ;
>
> sw_off:         clrf    PORTA                   ;turn LED off (this is the step you forgot!)
; Change label above to sw_off
>                goto    start                   ;
>
Which leads me to a Question for the OP: Do you use a pull up resitor on
RA.1?
Also, read up a bit on "switch debouncing". (I think it is discuss
somewhere on piclist.com)

Quentin

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