PIC18F4520-I/P Microchip Technology Inc., PIC18F4520-I/P Datasheet - Page 92

• Manufacturer Part Number: PIC18F4520-I/P
• Description: 40 Pin, 32 KB Flash, 1536 RAM, 36 I/O
• Manufacturer: Microchip Technology Inc.

Specifications of PIC18F4520-I/P

• A/d Inputs: 13-Channel, 10-Bit
• Comparators: 2
• Cpu Speed: 10 MIPS
• Eeprom Memory: 256 Bytes
• Input Output: 36
• Interface: I2C/SPI/USART
• Memory Type: Flash
• Number Of Bits: 8
• Package Type: 40-pin PDIP
• Programmable Memory: 32K Bytes
• Ram Size: 1.5K Bytes
• Speed: 40 MHz
• Timers: 1-8-bit, 3-16-bit
• Voltage, Range: 2-5.5 V
• Lead Free Status / Rohs Status: RoHS Compliant part Electrostatic Device

PIC18F2420/2520/4420/4520
Example 8-3 shows the sequence to do a 16 x 16
unsigned multiplication. Equation 8-1 shows the
algorithm that is used. The 32-bit result is stored in four
registers (RES3:RES0).
EQUATION 8-1:
EXAMPLE 8-3:
Example 8-4 shows the sequence to do a 16 x 16
signed multiply. Equation 8-2 shows the algorithm
used. The 32-bit result is stored in four registers
(RES3:RES0). To account for the sign bits of the argu-
ments, the MSb for each argument pair is tested and
the appropriate subtractions are done.
DS39631A-page 90
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
=
=
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
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
;
;
;
8
8
16
) +
) +
) +
Preliminary
EQUATION 8-2:
EXAMPLE 8-4:
RES3:RES0 = ARG1H:ARG1L ARG2H:ARG2L
;
;
;
;
;
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 ARG2H 2
(ARG1H ARG2L 2
(ARG1L ARG2H 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
 2004 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
) +
)