PIC18CXX2
EXAMPLE 6-4: 16 x 16 SIGNED MULTIPLY
ROUTINE
MOVFF
MULWF
ARG1L, WREG
ARG2L
; ARG1L * ARG2L ->
PRODH:PRODL
;
MOVFF
MOVFF
PRODH, RES1 ;
PRODL, RES0 ;
;
;
MOVFF
MULWF
ARG1H, WREG
ARG2H
; ARG1H * ARG2H ->
PRODH:PRODL
;
MOVFF
MOVFF
PRODH, RES3 ;
PRODL, RES2 ;
MOVFF
MULWF
ARG1L, WREG
ARG2H
; ARG1L * ARG2H ->
;
PRODH:PRODL
MOVFF
ADDWF
MOVFF
ADDWFC
CLRF
PRODL, WREG ;
RES1, F
; Add cross
PRODH, WREG ;
products
RES2, F
WREG, F
RES3, F
;
;
;
ADDWFC
;
MOVFF
MULWF
ARG1H, WREG ;
ARG2L ; ARG1H * ARG2L ->
;
PRODH:PRODL
MOVFF
ADDWF
MOVFF
ADDWFC
CLRF
PRODL, WREG ;
RES1, F
; Add cross
PRODH, WREG ;
products
RES2, F
WREG, F
RES3, F
;
;
;
ADDWFC
;
;
BTFSS
GOTO
MOVFF
SUBWF
MOVFF
SUBWFB
ARG2H, 7
SIGN_ARG1
ARG1L, WREG ;
RES2
ARG1H, WREG ;
RES3
; ARG2H:ARG2L neg?
; no, check ARG1
;
SIGN_ARG1
BTFSS
GOTO
ARG1H, 7
CONT_CODE
; ARG1H:ARG1L neg?
; no, done
MOVFF
SUBWF
MOVFF
SUBWFB
;
ARG2L, WREG ;
RES2
ARG2H, WREG ;
RES3
;
CONT_CODE
:
7/99 Microchip Technology Inc.
Preliminary
DS39026B-page 63
MICROCHIP [ MICROCHIP ]
