Hola:
Necesitaba una rutina de multiplicacion de 16x16 y encontré una nota de aplicación de microchip AN526 en donde se describe una rutina para la serie 16C5x.
Decidí probarla pero tiene errores: la multiplicación de 1FF x 7FFF debería ser 00FF 7E01, sin embargo el resultado que me da es 7FFD7E01.
Aparentemente el error aparece en la subrutina D_ADD, porque si se le sacan las referencias al registro FLAGS funciona bien para valores chicos, pero falla para los valores grandes. Sin embargo asi como está falla en los valores chicos, pero funciona para grandes valores como F000xFFFF
Alguien sabe qué esta pasando??
Les dejo el listado o lo pueden descargar de ww1.microchip.com/downloads/en/AppNotes/00526.zip
y utilizar el archivo dbl_MPYS.asm
PD:Lo probé con signed=true y con signed=false y no anda de ninguna forma
LIST P = 16C54, n = 66
;
;*******************************************************************
; Double Precision Multiplication
;
; ( Optimized for Code Size : Looped 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 : 033
; Clock Cycles : 333
;
; 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 ").
;
; The performance specs are for Unsigned arithmetic ( i.e,
; with "SIGNED equ FALSE ").
;
;
; Program: DBL_MPYS.ASM
; Revision Date:
; 1-13-97 Compatibility with MPASMWIN 1.40
;
;*******************************************************************;
;
ACCaLO equ 0x10
ACCaHI equ 0x11
ACCbLO equ 0x12
ACCbHI equ 0x13
ACCcLO equ 0x14
ACCcHI equ 0x15
ACCdLO equ 0x16
ACCdHI equ 0x17
temp equ 0x18
sign equ 0x19
Flags equ 0x1F
;
include "p16c5x.inc"
PIC54 equ 1FFH ; Define Reset Vector
TRUE equ 1
FALSE equ 0
MSB equ 7
org 0
;*******************************************************************
SIGNED equ TRUE ; 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.
;*******************************************************************
; Double Precision Addition ( ACCb + ACCa -> ACCb )
;
D_add bcf Flags,C ;Clear temp Carry bit
movf ACCaLO,W ; Addition ( ACCb + ACCa -> ACCb )
addwf ACCbLO, F ;add lsb
btfsc STATUS,C ;add in carry
incf ACCbHI, F
btfsc STATUS,C
bsf Flags,C
movf ACCaHI,W
addwf ACCbHI, F ;add msb
btfsc Flags,C
bsf STATUS,C
retlw 0
;*******************************************************************
; 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_mpyS ;results in ACCb(16 msb's) and ACCc(16 lsb's)
;
IF SIGNED
CALL S_SIGN
ENDIF
;
call setup
mloop rrf ACCdHI, F ;rotate d right
rrf ACCdLO, F
btfsc STATUS,C ;need to add?
call D_add
rrf ACCbHI, F
rrf ACCbLO, F
rrf ACCcHI, F
rrf ACCcLO, F
decfsz temp, F ;loop until all bits checked
goto mloop
;
IF SIGNED
btfss sign,MSB
retlw 0
comf ACCcLO, F ; negate ACCa ( -ACCa -> ACCa )
incf ACCcLO, F
btfsc STATUS,Z
decf ACCcHI, F
comf ACCcHI, F
btfsc STATUS,Z
neg_B comf ACCbLO, F ; negate ACCb
incf ACCbLO, F
btfsc STATUS,Z
decf ACCbHI, F
comf ACCbHI, F
retlw 0
ELSE
retlw 0
ENDIF
;
;*******************************************************************
;
setup movlw .16 ; for 16 shifts
movwf temp
movf ACCbHI,W ;move ACCb to ACCd
movwf ACCdHI
movf ACCbLO,W
movwf ACCdLO
clrf ACCbHI
clrf ACCbLO
retlw 0
;
;*******************************************************************
;
neg_A comf ACCaLO, F ; negate ACCa ( -ACCa -> ACCa )
incf ACCaLO, F
btfsc STATUS,Z
decf ACCaHI, F
comf ACCaHI, F
retlw 0
;
;*******************************************************************
; Assemble this section only if Signed Arithmetic Needed
;
IF SIGNED
;
S_SIGN movf ACCaHI,W
xorwf ACCbHI,W
movwf sign
btfss ACCbHI,MSB ; if MSB set go & negate ACCb
goto chek_A
;
comf ACCbLO, F ; negate ACCb
incf ACCbLO, F
btfsc STATUS,Z
decf ACCbHI, F
comf ACCbHI, F
;
chek_A btfss ACCaHI,MSB ; if MSB set go & negate ACCa
retlw 0
goto neg_A
;
ENDIF
;
;*******************************************************************
; Test Program
;*******************************************************************
; Load constant values to ACCa & ACCb for testing
;
main movlw 1
movwf ACCaHI
movlw 0FF ; loads ACCa = 01FF
movwf ACCaLO
;
movlw 0x7F
movwf ACCbHI
movlw 0xFF ; loads ACCb = 7FFF
movwf ACCbLO
;
call D_mpyS ; Here (ACCb,ACCc) = 00FF 7E01
;
self goto self
;
org PIC54
goto main
END
;****************************************************************
