One way to decide is the number of lines of messy tests versus a 256-entry table.  This problem is similar to identifying whether a recieved char is a number, a lowercase letter, or an uppercase letter.  Let's say you wanted to output the character to a 7-seg dispaly, and you had a table for the letter shapes.  You could do a big table with shapes for everything you wanted, and a ? for anything else, or do the messy test business first.  I chose the messy test version, because it was a lot shorter for what I needed.  Including overhead, my letter-and-number parser was about 120 lines including character shape tables,  half of what a full 256-line ascii shape table would have taken.

alice


> Hi all,
> I currently have an application where in the comms receive
> handler, I test the received command byte and branch off
> to other places depending on the value. As the values are
> not consecutive, is there a better way to test them than just
> doing the following time after time?
>
> ...
> movf    rx_cmd,w        ;get the received command byte
> xorlw   msg_eg1 ;compare with msg_eg1 (a constant)
> btfsc   zero            ;is it msg_eg1 ?
> goto    rx_eg1          ;yes, jump to that handler
> ...
>
> Block repeats for as many test cases as I need.
> It just seems ugly - is there a better/shorter way?
> The msg constants are all over the place value wise.
> I can't arrange them to be in continuous blocks.
> Regards...
>
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