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Within these pages, you can find many useful pieces of code mostly in assembly for the Microchip PIC micro controller family. A lot of people have spend many hours trying to put the bits and bytes together. If the code is NOT written by a member of the PCB Heaven community, then a link will be added above the code with the original website that this code was found.
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View code
16bit X 8bit
Author: Dingbat
This code was originally located @ http://www.piclist.com
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;--------------------------------------------------------------------+
; Function: Math : Multiply 16bits by 8bits |
;--------------------------------------------------------------------|
; Filename: M_MUL16x8.inc | Environment : MPLAB |
; Version : 1 | Microcontroller: PIC16F8x* |
; Date : 21/07/2003 | OSC MHz/MIPS : xx / xxx |
;--------------------------------------------------------------------|
; Author : Dingbat |
; Company : - |
; Files required : none |
;--------------------------------------------------------------------|
; Unsigned 16*8 bit Multiply AA(16) * BB(8), Result (CC) is 24bit
; adapted from code found on www.piclist.com
;
; params
; AA 0:1 (MSB:LSB) = number to multiply (16bit)
; BB = multiplier (8bit)
; CC 0:3 (MSB:LSB) = Product (24bit)
;
; Taking out the loops and inlining the code would save about
; another 20-30 instructions
MUL16x8
clrf CC+0 ;clear result
clrf CC+1 ;
clrf CC+2 ;
movlw .8
movwf bitCount ;bit counter set @ number of bits in multiplier
mul_L1 ;main loop here
rlf CC+2,f ;rotate result left (*2)
rlf CC+1,f ;
rlf CC+0,f ;
bcf CC+2,0 ;clear LSB of result after rotation
btfss BB,7 ;test msb of multipier
goto dontAdd ;if bit is clear then dont add
movfw AA+1 ;Add the 16 bits of AA to product
addwf CC+2,f ;
skpnc ;
incf CC+1,f ;
movfw AA ;
addwf CC+1,f ;
skpnc ;
incf CC+0,f ;
dontAdd
rlf BB,f ;rotate multiplier left
decfsz bitCount,f ;chk if finished all bits in multiplier
goto mul_L1
return |
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