The PICList code generator: Multiplication and Division by any Constant through a simple html form
Binary Multiplication by a Constant
8 bits by any constant by Myke Predko
See Division Methods for divide by 10, etc...
Since rotating any binary value one place left or right will multiply or
divide by 2:
;Multiply 8 bit ACC by 2 (double)
rlf ACC, f
;Multiply 16 bit ACC by 2 (double)
clrc
rlf ACC0, f
rlf ACC1, f
;Divide 8 bit ACC by 2 (half)
rrf ACC, f
;Divide 16 bit ACC by 2 (half)
clrc
rrf ACC0, f
rrf ACC1, f
; 28/32-bit unsigned Multiply by 16
; by Martin Sturm 2010
;
; Left shift by 4 with zero fill on right
; NOTE: discards uppermost bits shifted out
; 2 instructions shorter than unrolled RLF
; 1 instruction longer than code generator but can tolerate
; non-zero bits in the upper nibble of high byte
; Can be easily modified for 24, 16 bit versions
;
; 17 instructions, 17 cycles
MULT_U12_BY16 MACRO x4,x3,x2,x1
; x4 x3 x2 x1 W
; a b c d e f g h
MOVLW 0x0F ; 0x0F
ANDWF x4,F ; 0 b
SWAPF x4,F ; b 0
SWAPF x3,F ; d c
ANDWF x3,W ; 0 c
IORWF x4,F ; b c
XORWF x3,F ; d 0
;stop here for 16bit
MOVLW 0x0F ; 0x0F
SWAPF x2,F ; f e
ANDWF x2,W ; 0 e
IORWF x3,F ; d e
XORWF x2,F ; f 0
;stop here for 24bit
MOVLW 0x0F ; 0x0F
SWAPF x1,F ; h g
ANDWF x1,W ; 0 g
IORWF x2,F ; f g
XORWF x2,F ; h 0
;repeat the 5 inst. pattern above for larger datatypes
ENDM ; b c d e f g h 0
; 32-bit unsigned Divide by 16
; by Martin Sturm 2010
;
; Right shift 4byte value by 4 with zero fill on left.
; 2 instructions shorter than unrolled RLF implementation
; 1 instruction faster than code generator !
; Can be easily modified for 24, 16 bit versions
;
; 17 instructions, 17 cycles
DIV_U32_BY16 MACRO x4,x3,x2,x1
; x4 x3 x2 x1 W
; a b c d e f g h
MOVLW 0xF0 ; 0xF0
ANDWF x1,F ; g 0
SWAPF x1,F ; 0 g
SWAPF x2,F ; f e
ANDWF x2,W ; f 0
IORWF x1,F ; f g
XORWF x2,F ; 0 e
;stop here for 16bit
MOVLW 0xF0 ; 0xF0
SWAPF x3,F ; d c
ANDWF x3,W ; d 0
IORWF x2,F ; d e
XORWF x3,F ; 0 c
;stop here for 24bit
MOVLW 0xF0 ; 0xF0
SWAPF x4,F ; b a
ANDWF x4,W ; b 0
IORWF x3,F ; b c
XORWF x4,F ; 0 a
;repeat the 5 inst. pattern above for larger datatypes
ENDM ; 0 a b c d e f g
;****************************************************************************** ;Multiply 32 bit number by 10 ; for PIC18F by VegiePete gmail ;Inline code, in place result ;FSR0 points to 32 bit number (low byte in low memory) ;Returns overflow byte in WREG, Z set if no overflow Times10: movf POSTINC0,w ;grab 1st digit, point to 2nd mullw 10 movf POSTDEC0,w ;rescue 2nd digit, point to first movff PRODL,POSTINC0 ;save result low, point to 2nd movff PRODH,INDF0 ;save result high mullw 10 movf PRODL,w ;grab result low byte addwf POSTINC0,f ;add to highest previous byte, point tp 3rd movlw 0 addwfc PRODH,f ;propagate the carry movf INDF0,w ;rescue 3rd digit movff PRODH,INDF0 ;save result high mullw 10 movf PRODL,w ;grab result low byte addwfc POSTINC0,f ;add to highest previous byte, plus any carry movlw 0 addwfc PRODH,f ;propagate the carry movf INDF0,w ;rescue 4th digit movff PRODH,INDF0 ;save result high mullw 10 ;don't care about overflow byte movf PRODL,w ;grab result low byte addwfc INDF0,w ;add to highest previous byte, plus any carry movlw 0 addwfc PRODH,w ;propagate the carry, load overflow return
| file: /Techref/microchip/math/muldivconst.htm, 4KB, , updated: 2012/1/6 18:48, local time: 2025/10/31 05:43,
216.73.216.87,10-2-37-96:LOG IN
|
| ©2025 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/muldivconst.htm"> PIC Microcontoller Basic Math: Multiplication and Division by a Constant</A> |
| Did you find what you needed? |
|
PICList 2025 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 www.piclist.com! |
.