;*******************************************************************

;scale_hex2dec ; The purpose of this routine is to scale a hexadecimal byte to a ;decimal byte. In other words, if 'h' is a hexadecimal byte then ;the scaled decimal equivalent 'd' is: ; d = h * 100/256. ;Note that this can be simplified: ; d = h * 25 / 64 = h * 0x19 / 0x40 ;Multiplication and division can be expressed in terms of shift lefts ;and shift rights: ; d = [ (h<<4) + (h<<3) + h ] >> 6 ;The program divides the shifting as follows so that carries are automatically ;taken care of: ; d = (h + (h + (h>>3)) >> 1) >> 2 ; ;Inputs: W - should contain 'h', the hexadecimal value to be scaled ;Outputs: W - The scaled hexadecimal value is returned in W ;Memory: temp ;Calls: none scale_hex2dec mov temp, W ;Hex value is in W. clrb C ;Clear the Carry bit so it doesn't affect RRF ;Nikolai Golovchenko says: For better precision (especially for higher ;values of input byte), one more term should be added, so that ;d = (((h >> 3 + h) >> 3 + h) >> 1 + h) >> 2 = h * (1/4 + 1/8 + 1/64 + 1/512) ; ;This adds only 6 cycles, and reduces errors from 51 to 11 cases per ;all combinations of input (in both routines absolute errors are small,+-1). ; ; rr temp ; clrb C ; rr temp ; clrb C ; rr temp ; add temp, W rr temp clrb C rr temp clrb C rr temp ;temp = h>>3 add temp, W ;temp = h + (h>>3) rr temp ;temp = (h + (h>>3)) >> 1 add temp, W ;temp = h + ((h + (h>>3)) >> 1) rr temp clrb C mov W, >>temp ;d = W = (h + (h + (h>>3)) >> 1) >> 2 ret

file: /Techref/scenix/lib/math/scale/8bxpercent_sx.htm, 2KB, , updated: 2004/6/10 14:40, local time: 2024/6/22 04:48, |

©2024 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://piclist.com/techref/scenix/lib/math/scale/8bxpercent_sx.htm"> SX Microcontroller Math Method </A> |

Did you find what you needed? |

PICList 2024 contributors:
o List host: MIT, Site host massmind.org, Top posters @none found - 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 piclist.com! |

.