On Sat, 28 Oct 2000, Sean H. Breheny wrote:

> Hi all,
>
> The recent flurry of code challenges has piqued my interest and I have
> wanted to get in on it. Unfortunately, being very busy with school, I don't
> have much time, but I thought I would throw out two simple code challenges:
>
> 1) The object is to take a number in the range of 0x0 to 0xF in W and
> output the corresponding hex ASCII character 0 through 9 and A through F in
> W, without any temp registers. You may affect STATUS. My code does it in 4
> cycles,isochronous, with no return. No great accomplishment considering how
> simple the task, but I still ask, can anyone do it faster?

OTTOMH

    addlw    6
    skpndc
     addlw   'A'-('9'+1)
    addlw    '0'-6

PIC

4-cycles is the fastest I've seen for this.

>
> 2) Same thing, except we now want to take a number in the range of 0x00 to
> 0xFF in W and output two ASCII characters, the most significant character
> into CHAR_HI and the least significant into W. No other registers can be
> used. (NOTE: To solve this you will need some kind of routine to swap
> CHAR_HI and W, as far as I can tell. I came up with a 3 cycle one, and then
> found out that it was already listed on www.piclist.com. It would be
> interesting to see if there are others).

    movwf  char_hi
    swapf  char_hi,w
    andlw  0x0f

    addlw  6
    skpndc
     addlw   'A'-('9'+1)
    addlw    '0'-6

    xorwf  char_hi,w
    xorwf  char_hi,f
    xorwf  char_hi,w

    andlw  0x0f

    addlw  6
    skpndc
     addlw   'A'-('9'+1)
    addlw    '0'-6

>
> My resulting code is 15 cycles, isochronous

Hmm, so is mine. But I bet Dmitry or Nikolai has a 12-cycle solution.

Scott

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