On Thu, 2006-02-23 at 06:48 -0800, Peter van Hoof wrote:

> look at app note an544
> http://www.microchip.com/stellent/idcplg?IdcService=SS_GET_PAGE&nodeId=1824&appnote=en011088
>
>
> there are 4 ways described to do this without tables
> fastest: Binary to BCD (8 bit) 10 words  62 cycles 1 byte scratch  unused

When Peter says that the fastest way to solve this problem without tables
takes 62 cycles, what he really means is that the fastest way an544 solves
this problem takes 62 cycles. Of course, there are faster non-table
solutions out there. One in particular takes 18 cycles.

        SWAPF   bin, W 		;w  = A0*16+A1
        ADDWF   bin, W 		;w  = A0+A1
        ANDLW   00001111b 	;w  = A0+A1 % 16
        SKPNDC 			;if A0+A1 > 16
         ADDLW  0x16 		;  w  += 16
        SKPNDC 			;if w % 16 > 10
         ADDLW  0x06 		;  w  += 6
        ADDLW   0x06 		;w  += 6
        SKPDC 			;if w < 10
         ADDLW  -0x06 		;  w  -= 6

        BTFSC   bin,4
         ADDLW   0x16 - 1 + 0x6
        SKPDC
         ADDLW  -0x06

        BTFSC   bin, 5
         ADDLW  0x30

        BTFSC   bin, 6
         ADDLW  0x60

   ; result is in W

This was adapted from:
http://www.piclist.com/techref/microchip/math/radix/b2bhp-8b3d.htm
And the algorithm is described:
http://www.piclist.com/techref/method/math/radixs.htm

Scott
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