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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
24bit X 8bit
Author: Byron A Jeff
This code was originally located @ http://www.piclist.com
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mult24x8:
clrf prod0 ; Clear the product
clrf prod1
clrf prod2
clrf prod3
clrf twofour3 ; Clear the top byte of the multiplicand
multloop:
movf eight,W ; Check to see if eight bit is empty
btfsc STATUS,Z ; Done if zero
return
bcf STATUS,C ; clear carry
rrl eight,F ; Get the next bit
btfss STATUS,C ; Add if carry is set
goto multshift ; shift only if 0
movf twofour0,W ; Add the 32 bits of multiplicand to product
addwf prod0,F ; each addwf sets the carry
btfsc STATUS,C ; Don't increment if no carry
call carryprop1 ; Propigate carry to next byte(s)
movf twofour1,W ;
addwf prod1,F ;
btfsc STATUS,C ; Don't increment if no carry
call carryprop2 ; Propigate carry to next byte(s)
movf twofour2,W ;
addwf prod2,F ;
btfsc STATUS,C ; Don't increment if no carry
incf prod3,F ; Add one to next byte if carry occured
movf twofour3,W ;
addwf prod3,F ;
multshift:
bcf STATUS,C ; clear carry
rlf twofour0,F ; Shift the 24 bits one bit to the left
rlf twofour1,F
rlf twofour2,F
rlf twofour3,F
goto multloop
carryprop1:
incfsz prod1,F
return
carryprop2:
incfsz prod2,F
return
carryprop3:
incf prod3,F
return
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