Hi!
26-Mar-98 15:42 Scott Dattalo wrote about "Re: Divide by 3 (by 5, by 10)":

 >> Vladimir M. Klochko wrote:
 >> > ;   Divide by 10
 >>  <snip>
 >> > ;;      23 words and 1 byte
                        ^^^^^^^


 >> Here's an 18 cycle Divide by 5:
 >>         ADDLW   1
 >>         SKPNC
 >>          RETLW  0x33
 >>
 >>         MOVWF   ql
    ....
 >>         ADDWF   qh,W

    I didn't analyse this code. It seems good. But...

    First of all, "18 cycles" is not quite true. :)
Since You use RETLW for some special case of input You must add
a RETURN to this code for any other cases. Of course, my
examples don't contain these RETURN's at all, but I don't imply
a subroutine. I prefer (when it's possible) to make some macros
for later usage. When I need a subroutine I can compose it using
such macro and return instruction. When I need it only once in
some program I can simple use the same macro in the program
(without "return").

    Another disadvantage is the TWO temporary bytes of RAM have
to be dedicated for this code (my examples use only ONE byte).
It doesn't cause a problem itself, but sometimes it is too
difficult to maintain the temporary memory space usage. In
reality it is a "compiled stack" (the same as the one provided
by advanced C compilers). To keep in mind the whole call-tree
(and manually rebuild it after any sorce change) is not an easy
task for human.   So, "the less temporary memory space the
better". :)    Sometimes I prefer even the slightly larger code
(to make an wide-used macros) if it requires the less RAM space
or no RAM at all. Of course, everybody has its own approach.

 >>
 >> Scott
 >>
 >> ---
 >>   If you believe everything you read then you shouldn't read.
 >>                                              Japanese Proverb
    Well.  Am I ready to read?   Am I ready to read Japanese? :)

--

                                    Vladimir M. Klochko