This IS on James web page. Or a should say that there's a variation that's
nearly identical. But as everyone knows, this isn't the fastest algorithm. ;).
However, you're on a good roll Martin and I wouldn't want to spoil your
fun. (The truth be told, I don't have time to explain it...)

Scott

On Thu, 6 Apr 2000, [iso-8859-1] Martin Schäfer wrote:

> Thank you, James,
> 
> now I found an 8x8 multiply from Andrew Warren. After eliminating the loop
> I think the following procedure is the fastest and not very long:
> 
> If anyone has a better one: I'm interested.
> 
> Martin
> 
> 
> 
> ;***************************************************************************
> ****
> ;**  time efficient multiplication 8 bit x 8 bit = 16 bit (unsigned)
> ;**
> ;**  company:       elektronik 21 GmbH
> ;**  programmer:            Martin Schaefer (idea from Andrew Warren)
> ;**
> ;**  execution time:  fixed 38 cycles  (with jump in and jump out) !!!
> ;**  code length:           35 words
> ;**  multiplier:            w
> ;**  multiplicand:    resultlo
> ;**  result:        resulthi:resultlo
> ;***************************************************************************
> ****
> MUL8X8   CODE
> Mul8x8                          ;* 2 cycles for call - instruction
>         GLOBAL Mul8x8, resulthi, resultlo
> 
> mult    MACRO
>         btfsc   STATUS,C
>         addwf   resulthi,F
>         rrf     resulthi,F
>         rrf     resultlo,F
>         ENDM
> 
>         clrf    resulthi                ;* 1 cycle
>         rrf     resultlo,F              ;* 1 cycle
> 
>         mult                            ;* 4 cycles
>         mult                            ;* 4 cycles
>         mult                            ;* 4 cycles
>         mult                            ;* 4 cycles
>         mult                            ;* 4 cycles
>         mult                            ;* 4 cycles
>         mult                            ;* 4 cycles
>         mult                            ;* 4 cycles
> 
>         retlw 0                 ;* 2 cycles
> ;***************************************************************************
> ****
>