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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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;*******************************************************************
; Double Precision Multiplication
;
; ( Optimized for Speed : straight Line Code )
;
;*******************************************************************;
; Multiplication : ACCb(16 bits) * ACCa(16 bits) -> ACCb,ACCc (
32
bits )
; (a) Load the 1st operand in location ACCaLO & ACCaHI ( 16
bits )
; (b) Load the 2nd operand in location ACCbLO & ACCbHI ( 16
bits )
; (c) CALL D_mpy
; (d) The 32 bit result is in location (
ACCbHI,ACCbLO,ACCcHI,ACCcLO )
;
; Performance :
; Program Memory : 240
; Clock Cycles : 233 (282)
;
; Note : The above timing is the worst case timing, when the
; register ACCb = FFFF. The speed may be improved if
; the register ACCb contains a number ( out of the
two
; numbers ) with less number of 1s.
;
; The performance specs are for Unsigned arithmetic (
i.e,
; with "SIGNED equ FALSE ").
;
; Program: DBL_MPYF.ASM
; Revision Date:
; 1-13-97 Compatibility with MPASMWIN
1.40
;
;*******************************************************************
SIGNED equ FALSE ; Set This To 'TRUE' if the
routines
; ; for Multiplication & Division
needs
; ; to be assembled as Signed Integer
; ; Routines. If 'FALSE' the above
two
; ; routines ( D_mpy & D_div ) use
; ; unsigned arithmetic.
;*******************************************************************
; multiplication macro
;
mulMac MACRO
LOCAL NO_ADD
;
rrf ACCdHI, F ;rotate d right
rrf ACCdLO, F
btfss STATUS,C ;need to add?
goto NO_ADD ; no addition necessary
movf ACCaLO,W ; Addition ( ACCb + ACCa -> ACCb )
addwf ACCbLO, F ;add lsb
btfsc STATUS,C ;add in carry
incf ACCbHI, F
movf ACCaHI,W
addwf ACCbHI, F ;add msb
NO_ADD rrf ACCbHI, F
rrf ACCbLO, F
rrf ACCcHI, F
rrf ACCcLO, F
;
ENDM
;
;*******************************************************************;
; Double Precision Multiply ( 16x16 -> 32 )
; ( ACCb*ACCa -> ACCb,ACCc ) : 32 bit output with high word
; in ACCb ( ACCbHI,ACCbLO ) and low word in ACCc ( ACCcHI,ACCcLO
).
;
D_mpyF ;results in ACCb(16 msb's) and
ACCc(16
lsb's)
;
IF SIGNED
CALL S_SIGN
ENDIF
;
call setup
;
; use the mulMac macro 16 times
;
;----------------------
; inserted by RAVI PAILOOR
movlw .16
movwf loopctr
;----------------------
loop mulMac
;----------------------
; inserted by RAVI PAILOOR
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