Scott Dattalo and Dmitry Kiryashov
;ascii1 and ascii2 are the tens and ones digit of a number we wish ;to convert to binary ; ; In C: ; ; binary = (ascii1 & 0xf) * 10 + (ascii2 & 0xf); ; ; (I'd be interested to see how a compiler would generate the asm for this.) ; movlw 0x0f andwf ascii2,f ;Clear the upper nibble of the one's digit ; Multiply the ones digit by 10. rlf ascii1,w ;2*tens ;Note that the carry is also cleared because ;ascii1 is an ASCII number between 0x30-0x39 andlw 0x1e ;Clear upper nibble of tens digit ;In addition, we clear the shifted in carry movwf ascii1 ;W = ascii1 = 2*original ascii1 rlf ascii1,f ;ascii1 = 4*original ascii1 rlf ascii1,f ;ascii1 = 8*original ascii1 addwf ascii1,w ;W = 2*original ascii1 + 8 *original ascii1 ; = 10*original ascii1 addwf ascii2,w ; ; Or use this one that saves a cycle: rlf tens,w andlw 0x1e ;w=2*tens movwf temp rlf temp,f ;temp=4*tens rlf temp,f ;temp=8*tens addwf ones,w addlw -'0' ;convert from ASCII to decimal ;w=tens*2 + ones addwf temp,w ;w=10*tens + ones ;Dmitry Kiryashov [zews at AHA.RU] says: ;Destructive way to save one more clock ;-) movfw tens ;*1 addwf tens,F ;*2 rlf tens,F ;*4 addwf tens,F ;*5 rlf tens,W ;*10 addwf ones,W addlw low -11.*'0' ;Why so ? tens is '0' + x , ones is '0' + y , where x and y are in range ;of 0..9 So finally '0'*(10+1)=48.*11.=528.=0x210 . it is constant so we ;can subtract it back from result. Here we gone ;)
|file: /Techref/microchip/math/radix/a2b-2d8b-sd.htm, 2KB, , updated: 2002/7/30 10:45, local time: 2018/7/19 16:18,
|©2018 These pages are served without commercial sponsorship. (No popup ads, etc...).Bandwidth abuse increases hosting cost forcing sponsorship or shutdown. This server aggressively defends against automated copying for any reason including offline viewing, duplication, etc... Please respect this requirement and DO NOT RIP THIS SITE. Questions?|
<A HREF="http://www.piclist.com/techref/microchip/math/radix/a2b-2d8b-sd.htm"> PIC Microcontoller Radix Math Method </A>
|Did you find what you needed?|
PICList 2018 contributors:
o List host: MIT, Site host massmind.org, Top posters @20180719 RussellMc, Van Horn, David, Sean Breheny, Isaac M. Bavaresco, David C Brown, Bob Blick, Neil, Denny Esterline, John Gardner, Brent Brown,
* Page Editors: James Newton, David Cary, and YOU!
* Roman Black of Black Robotics donates from sales of Linistep stepper controller kits.
* Ashley Roll of Digital Nemesis donates from sales of RCL-1 RS232 to TTL converters.
* Monthly Subscribers: Gregg Rew. on-going support is MOST appreciated!
* Contributors: Richard Seriani, Sr.
Welcome to www.piclist.com!