Andy David says:
Here's my 32 bit routine as written for the PIC 17c43 [ed: and converted to the Scenix SX] taken from a mail I sent Scott just after I wrote it, hence the comments about the implementations I used.Looks a lot like Scott's original 16-bit sqrt. As the root is going to be a 16 bit number the last subtract is awkward, so the 24-bit sqrt method wasn't appropriate. I did actually write this myself rather than automatically converting Scott's code to 32 bit. I DID, however, consciously and unashamedly steal two parts - how to carry out the final 17-bit subtraction and how to count iterations - the extra 'counting' bit in the mask was quite a devious idea. This one took a little longer to write than the 24-bit, probably because it needs to iterate more times...
Standard disclaimer applies
;========================================================================= ; brSQRT32 ; ; Calculates the square root of a thirtytwo bit number using the ; binary restoring method. ; ; Result in ACCaHI:ACCaLO ; Mask in ACCbHI:ACCbLO ; Input in ACCcHI:ACCcLO:ACCdHI:ACCdLO ; ; Takes between ... and ... cycles (incl. call and return). ; Uses 66 words ROM, 8 bytes RAM including 4 holding the input. ; ;------------------------------------------------------------------------- brSQRT32: mov W, #$40 ; Initial value for Result is... mov ACCaHI, W ; ... 01000000 00000000 clr ACCaLO ; mov W, #$C0 ; Initial value for mask is... mov ACCbHI, W ; ... 11000000 00000000 clr ACCbLO ; (second '1' is loop counter). Sub_Cmp: mov W, ACCaLO ; Compare root-so-far with current sub ACCcLO, W ; ... remainder. mov W, ACCaHI ; sb C movsz W, ++ACCaHI ; sub ACCcHI, W ; sb C ; jmp brstr ; (result is negative, need to restore). In1: mov W, ACCbLO ; set the current bit in the result. or ACCaLO, W ; mov W, ACCbHI ; or ACCaHI, W ; ShftUp: rl ACCdLO ; rl ACCdHI ; rl ACCcLO ; rl ACCcHI ; rr ACCbHI ; Shift mask right for next bit, whilst rr ACCbLO ; ... shifting IN MSB from remainder. snb ACCbHI.7 ; If MSB is set, unconditionally set the jmp USet1 ; ... next bit. mov W, ACCbLO ; Append '01' to root-so-far xor ACCaLO, W ; mov W, ACCbHI ; xor ACCaHI, W ; sb C ; If second '1' in mask is shifted out, jmp Sub_Cmp ; ... then that was the last normal iteration. mov W, ACCaLO ; Last bit Generation. sub ACCcLO, W ; ... The final subtract is 17-bit (15-bit root mov W, ACCaHI ; ... plus '01'). Subtract 16-bits: if result sb C movsz W, ++ACCaHI sub ACCcHI, W ; ... generates a carry, last bit is 0. sb C ; ret mov W, #1 ; If result is 0 AND msb of is '0', result bit snb Z ; ... is 0, otherwise '1'. snb ACCdHI.7 ; xor ACCaLO, W ; ret USet1: snb C ; If mask has shifted out, leave. final bit ret ; ... has been set by iorwf at in1. clrb ACCbHI.7 ; clear bit shifted in from input. mov W, ACCbLO ; Append '01' to root-so-far xor ACCaLO, W ; mov W, ACCbHI ; xor ACCaHI, W ; mov W, ACCaLO ; This subtraction is guaranteed not to sub ACCcLO, W ; ... cause a borrow, so subtract and mov W, ACCaHI ; ... jump back to insert a '1' in the sb C movsz W, ++ACCaHI sub ACCcHI, W ; ... root. jmp In1 ; brstr: mov W, ACCaLO ; A subtract above at Sub_Cmp was -ve, so add ACCcLO, W ; ... restore the remainder by adding. mov W, ACCaHI ; The current bit of the root is zero. snb C movsz W, ++ACCaHI add ACCcHI, W ; jmp ShftUp ;
file: /Techref/SCENIX/lib/math/sqrt/sqrt32_sx.htm, 5KB, , updated: 2004/6/10 14:40, local time: 2024/8/14 18:52,
18.190.239.122:LOG IN
|
©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://sxlist.com/TECHREF/SCENIX/lib/math/sqrt/sqrt32_sx.htm"> SX Microcontroller Math Method - 32 bit Square Root binary restoring method</A> |
Did you find what you needed? |
Welcome to sxlist.com!sales, advertizing, & kind contributors just like you! Please don't rip/copy (here's why Copies of the site on CD are available at minimal cost. |
Welcome to sxlist.com! |
.