Hi,

Looks like just another useful code snipped - not used more then 2 K
PIC4s till now.
but...

Dmitry Kiryashov wrote:

>
> Hello. Probably you ask about the following construction...
>
> WBR Dmitry.
>
>         movlw   0                       ;for instance zero
>         call    subroutine_switcher     ;function is called
>         movlw   1
>         call    subroutine_switcher
> ;...
> ;       continue here
> ;...
>

Dmitry, can you please give me an hint what Idea is behind the following
shortcut-math ?
I recognize it will calculate the address for setting the appropriate PC
for the subroutine, but how does it work ?? ( I never used xor for doing
a something like an n * 4  before ).

> switcher_to_subroutines:
>         movwf   pclath
>         xorlw   high    ($+4)
>         xorwf   pclath,f
>         xorlw   high    ($+2)
>         addwf   pcl,f
>
> ;function_0 is here
>
>         movlw   high    function_0      ;probably isn't required
>         movwf   pclath                  ;in 2K PICs
>         movlw   low     function_0
>         movwf   pcl
>
> ;function_1 is here
>
>         movlw   high    function_1
>         movwf   pclath
>         movlw   low     function_1
>         movwf   pcl
>
> ;etc...
>
> function_0:
> ;...
> ;       function_0 program body
> ;...
>         return