PIC18F2331-E/ML MICROCHIP [Microchip Technology], PIC18F2331-E/ML Datasheet - Page 96

• Manufacturer Part Number: PIC18F2331-E/ML
• Description: 28/40/44-Pin Enhanced Flash Microcontrollers with nanoWatt Technology, High-Performance PWM and A/D
• Manufacturer: MICROCHIP [Microchip Technology]

PIC18F2331/2431/4331/4431
Example 9-3
unsigned multiply.
that is used. The 32-bit result is stored in four registers,
RES<3:0>.
EQUATION 9-1:
EXAMPLE 9-3:
Example 9-4
signed multiply.
used. The 32-bit result is stored in four registers,
RES<3:0>. To account for the sign bits of the argu-
ments, each argument pair’s Most Significant bit (MSb)
is tested and the appropriate subtractions are done.
DS39616D-page 96
RES<3:0>
;
;
;
MOVF
MULWF
MOVFF
MOVFF
MOVF
MULWF
MOVFF
MOVFF
MOVF
MULWF
MOVF
ADDWF
MOVF
ADDWFC RES2, F
CLRF
ADDWFC RES3, F
MOVF
MULWF
MOVF
ADDWF
MOVF
ADDWFC RES2, F
CLRF
ADDWFC RES3, F
ARG1L, W
ARG2L
PRODH, RES1
PRODL, RES0
ARG1H, W
ARG2H
PRODH, RES3
PRODL, RES2
ARG1L, W
ARG2H
PRODL, W
RES1, F
PRODH, W
WREG
ARG1H, W
ARG2L
PRODL, W
RES1, F
PRODH, W
WREG
shows the sequence to do a 16 x 16
shows the sequence to do a 16 x 16
=
=
Equation 9-2
Equation 9-1
ARG1H:ARG1L  ARG2H:ARG2L
(ARG1H  ARG2H  2
(ARG1H  ARG2L  2
(ARG1L  ARG2H  2
(ARG1L  ARG2L)
16 x 16 UNSIGNED
MULTIPLICATION
ALGORITHM
16 x 16 UNSIGNED
MULTIPLY ROUTINE
; ARG1L * ARG2L ->
; PRODH:PRODL
;
;
; ARG1H * ARG2H ->
; PRODH:PRODL
;
;
; ARG1L * ARG2H ->
; PRODH:PRODL
;
; Add cross
; products
;
;
;
;
; ARG1H * ARG2L ->
; PRODH:PRODL
;
; Add cross
; products
;
;
;
shows the algorithm
shows the algorithm
8
8
16
) +
) +
) +
EQUATION 9-2:
EXAMPLE 9-4:
RES<3:0>
;
;
;
;
;
SIGN_ARG1
;
CONT_CODE
=
=
MOVF
MULWF
MOVFF
MOVFF
MOVF
MULWF
MOVFF
MOVFF
MOVF
MULWF
MOVF
ADDWF
MOVF
ADDWFC RES2, F
CLRF
ADDWFC RES3, F
MOVF
MULWF
MOVF
ADDWF
MOVF
ADDWFC RES2, F
CLRF
ADDWFC RES3, F
BTFSS
BRA
MOVF
SUBWF
MOVF
SUBWFB RES3
BTFSS
BRA
MOVF
SUBWF
MOVF
SUBWFB RES3
:
ARG1H:ARG1L  ARG2H:ARG2L
(ARG1H  ARG2H  2
(ARG1H  ARG2L  2
(ARG1L  ARG2H ² 2
(ARG1L  ARG2L)+
(-1  ARG2H<7>  ARG1H:ARG1L  2
(-1  ARG1H<7>  ARG2H:ARG2L  2
ARG1L, W
ARG2L
PRODH, RES1 ;
PRODL, RES0 ;
ARG1H, W
ARG2H
PRODH, RES3 ;
PRODL, RES2 ;
ARG1L,W
ARG2H
PRODL, W
RES1, F
PRODH, W
WREG
ARG1H, W
ARG2L
PRODL, W
RES1, F
PRODH, W
WREG
ARG2H, 7
SIGN_ARG1
ARG1L, W
RES2
ARG1H, W
ARG1H, 7
CONT_CODE
ARG2L, W
RES2
ARG2H, W
16 x 16 SIGNED
MULTIPLICATION
ALGORITHM
16 x 16 SIGNED MULTIPLY
ROUTINE
 2010 Microchip Technology Inc.
; ARG1H * ARG2H ->
; ARG1L * ARG2H ->
;
; Add cross
; products
;
;
;
;
; ARG1H * ARG2L ->
;
; Add cross
; products
;
;
;
; ARG2H:ARG2L neg?
; no, check ARG1
;
;
;
; ARG1H:ARG1L neg?
; no, done
;
;
;
; ARG1L * ARG2L ->
; PRODH:PRODL
; PRODH:PRODL
; PRODH:PRODL
; PRODH:PRODL
8
8
16
) +
) +
) +
16
16
) +
)