> > What about a "goto $" at the end?
> 
> What happens with a "goto $"?

The code below will not stop after the movwf portc, and probably
wrap around to the start vector (after executing many addlw 0xff).
goto $ will make it wait in a loop. goto $x adds x to the PC. So

goto $+2 jumps over the next instruction (16F or less) etc
goto $-2 jumps over the previous instruction (16F or less) etc

goto $ should be used with caution. Usually safe if you're in a
particular fixed loop, eg next, but beware of inserting code
into goto $ loops

btfss adcon0,go_done
goto $-1  ;loop until adcon0,go_done = 1 ; 16F

btfss adcon0,go_done
goto $-2  ;loop until adcon0,go_done = 1 ; 18F

goto $ can be written as goto $-0 or goto $+0 (not goto $0)

movlw b'00000000' ;
tris porta ;
tris portb ;
tris portc ;

movlw b'11111111' ;
movwf porta ;
movwf portb ;
movwf portc ;

wait  goto wait  ; goto $ or goto $+0

END ;

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