; by Rich Leggitt with tweaks by Scott Dattalo and bugfix by Dmitry Kiryashov and Nikolai Golovchenko ; given 16 bit data in HI and LO, extract decimal digits ; requires one Output register called temp, HI and LO are destroyed. ; 42 instructions and less than 269 (or 252 with known_zero) instructions executed clrf temp goto $+2 ;[NG] was: skip sub10k incf temp,f movlw 10000 & 255 subwf LO,f ;Scott Dattalo says: ;If you have a ram location that's known to be zero, then ;the following [the IF] can be replaced with [the ELSE] IFNDEF known_zero movlw 10000 >> 8 skpc movlw (10000>>8)+1 ;[NG] was: addlw 1 ; this sucks subwf HI,f ELSE rlf known_zero,W sublw (10000>>8)+1 ;bugfix by Dmitry Kiryashov and Nikolai Golovchenko subwf Hi,F ENDIF bc sub10k ;9*7=63/8*7=56 inst in loop for 60900 (worst) output(temp); movlw 10 movwf temp add1K decf temp,f movlw 1000 & 255 addwf LO,f ;Scott Dattalo says: ;If you have a ram location that's known to be zero, then ;the following [the IF] can be replaced with [the ELSE] IFNDEF known_zero movlw 1000 >> 8 skpnc movlw (1000>>8)+1 ;[NG] was: addlw 1 addwf HI,f ELSE rlf known_zero,w addlw 1000 >> 8 addwf HI,f ENDIF bnc add1k ;9*10=90/8*10=80 inst in loop for 60900 output(temp); ;Scott takes over here clrf temp movlw 100 goto $+2 ;[NG] was: skip sub100 incf temp,f subwf LO,f skpnc ;[NG] was: skpc goto sub100 decf HI,f btfss HI,7 ;Check msb instead of carry for underflow. goto sub100 ;4 inst per loop to 200 then 7 per loop to 900. ;Total 64(?) in loop for worst case ;at this point, HI = 0xff, and 0 <= LO <= 99 output(temp) movlw 10 movwf temp add10 decf temp,f addwf LO,f bnc add10 ;40 inst in loop for worst case. output(temp); output(LO); return
|file: /Techref/microchip/math/radix/b2a-16b5a-rl.htm, 3KB, , updated: 2002/10/31 15:57, local time: 2018/11/14 04:24,
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<A HREF="http://www.piclist.com/techref/microchip/math/radix/b2a-16b5a-rl.htm"> PIC Microcontoller Radix Math Method </A>
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