PIC18F25J50 MICROCHIP [Microchip Technology], PIC18F25J50 Datasheet - Page 114

• Manufacturer Part Number: PIC18F25J50
• Description: 28/44-Pin, Low-Power, High-Performance USB Microcontrollers with nanoWatt XLP Technology
• Manufacturer: MICROCHIP [Microchip Technology]

PIC18F46J50 FAMILY
Example 8-3
16 x 16 unsigned multiplication.
the algorithm that is used. The 32-bit result is stored in
four registers (RES<3:0>).
EQUATION 8-1:
EXAMPLE 8-3:
Example 8-4
signed multiply.
used. The 32-bit result is stored in four registers
(RES<3:0>). To account for the sign bits of the
arguments, the MSb for each argument pair is tested
and the appropriate subtractions are done.
DS39931D-page 114
RES3:RES0
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
provides the instruction sequence for a
provides the sequence to do a 16 x 16
=
=
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
Equation 8-2
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
provides the algorithm
Equation 8-1
; ARG1L * ARG2L->
; PRODH:PRODL
;
;
; ARG1H * ARG2H->
; PRODH:PRODL
;
;
; ARG1L * ARG2H->
; PRODH:PRODL
;
; Add cross
; products
;
;
;
;
; ARG1H * ARG2L->
; PRODH:PRODL
;
; Add cross
; products
;
;
;
8
8
16
) +
) +
) +
provides
EQUATION 8-2:
EXAMPLE 8-4:
RES3:RES0
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
=
=
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
ARG1H:ARG1L · ARG2H:ARG2L
(ARG1H · ARG2H · 2
(ARG1H · ARG2L · 2
(ARG1L · ARG2H · 2
(ARG1L · ARG2L) +
(-1 · ARG2H<7> · ARG1H:ARG1L · 2
(-1 · ARG1H<7> · ARG2H:ARG2L · 2
16 x 16 SIGNED
MULTIPLICATION
ALGORITHM
16 x 16 SIGNED MULTIPLY
ROUTINE
 2011 Microchip Technology Inc.
; ARG1L * ARG2L ->
; PRODH:PRODL
;
;
; ARG1H * ARG2H ->
; PRODH:PRODL
;
;
; ARG1L * ARG2H ->
; PRODH:PRODL
;
; Add cross
; products
;
;
;
;
; ARG1H * ARG2L ->
; PRODH:PRODL
;
; Add cross
; products
;
;
;
; ARG2H:ARG2L neg?
; no, check ARG1
;
;
;
; ARG1H:ARG1L neg?
; no, done
;
;
;
8
8
16
) +
) +
) +
16
16
) +
)