On Thu, Jun 26, 2003 at 05:13:46PM +0100, Sergio Masci wrote:
> From: Daniel Serpell <daniel@ATMLAB.UTFSM.CL>
>
> Assuming that this is actually giving you what you want and that acc is 16 bits,
> the first 3 iterations of the loop can be perfomed on 8 bit acc and the
> remainder on 16 bit acc. Also your lookup table will require 256 entries

I'm not thinking on using lookup tables. The code will be:

; This code is under the GNU LGPL License,
; see http://www.gnu.org/copyleft/lesser.html

cbits   MACRO data
        rrf     data,W
        andlw   0x55
        subwf   data,F
        movlw   0x33
        andwf   data,W
        addwf   data,F
        rrf     data,F
        addwf   data,F
        rrf     data,F
        swapf   data,W
        addwf   data,W
        andlw   0x0F

        ENDM

add8val:

        clrf    acch

        cbits   data0
        movwf   accl    ; max = 8
        cbits   data1
        rrlf    accl,F
        addwf   accl,F  ; max = 24
        cbits   data2
        rrlf    accl,F
        addwf   accl,F  ; max = 56
        cbits   data3
        rrlf    accl,F
        addwf   accl,F  ; max = 120
        cbits   data4
        rrlf    accl,F
        addwf   accl,F  ; max = 248
        cbits   data5
        rrlf    accl,F
        rrlf    acch,F
        addwf   accl,F
        btfsc   STATUS,C
        incf    acch,F  ; max = 504
        cbits   data6
        rrlf    accl,F
        rrlf    acch,F
        addwf   accl,F
        btfsc   STATUS,C
        incf    acch,F  ; max = 1016
        cbits   data7
        rrlf    accl,F
        rrlf    acch,F
        addwf   accl,F
        btfsc   STATUS,C
        incf    acch,F  ; max = 2040


That's exactly 121 cycles, and 121 program words.
But seeing it writen, I have found an error (try to spot it!),
so 7 more instructions are needed (with 128 cycles total).
The code can be expanded for more than 8 bits.

    Daniel.

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