PIC17C42 Microchip Technology, PIC17C42 Datasheet - Page 50

• Manufacturer Part Number: PIC17C42
• Description: High-Performance 8-Bit CMOS EPROM/ROM Microcontroller
• Manufacturer: Microchip Technology

PIC17C4X
Example 8-3 shows the sequence to do a 16 x 16
unsigned multiply. Equation 8-1 shows the algorithm
that is used. The 32-bit result is stored in 4 registers
RES3:RES0.
EQUATION 8-1:
RES3:RES0
DS30412C-page 50
=
=
(ARG1H * ARG2H * 2
(ARG1H * ARG2L * 2
(ARG1L * ARG2H * 2
(ARG1L * ARG2L)
ARG1H:ARG1L * ARG2H:ARG2L
16 x 16 UNSIGNED
MULTIPLICATION
ALGORITHM
8
8
16
)
)
) +
+
+
EXAMPLE 8-3:
;
;
;
MOVFP
MULWF
MOVPF
MOVPF
MOVFP
MULWF
MOVPF
MOVPF
MOVFP
MULWF
MOVFP
ADDWF
MOVFP
ADDWFC
CLRF
ADDWFC
MOVFP
MULWF
MOVFP
ADDWF
MOVFP
ADDWFC
CLRF
ADDWFC
ARG1L, WREG
ARG2L
PRODH, RES1 ;
PRODL, RES0 ;
ARG1H, WREG
ARG2H
PRODH, RES3 ;
PRODL, RES2 ;
ARG1L, WREG
ARG2H
PRODL, WREG ;
RES1, F
PRODH, WREG ;
RES2, F
WREG, F
RES3, F
ARG1H, WREG ;
ARG2L
PRODL, WREG ;
RES1, F
PRODH, WREG ;
RES2, F
WREG, F
RES3, F
16 x 16 MULTIPLY ROUTINE
1996 Microchip Technology Inc.
; ARG1L * ARG2L ->
;
; ARG1H * ARG2H ->
;
; ARG1L * ARG2H ->
;
; Add cross
;
;
;
; ARG1H * ARG2L ->
;
; Add cross
;
;
;
PRODH:PRODL
PRODH:PRODL
PRODH:PRODL
PRODH:PRODL
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