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PIC18LF4331-E/ML Datasheet(PDF) 96 Page - Microchip Technology |
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PIC18LF4331-E/ML Datasheet(HTML) 96 Page - Microchip Technology |
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96 / 392 page  PIC18F2331/2431/4331/4431 DS39616D-page 96 2010 Microchip Technology Inc. Example 9-3 shows the sequence to do a 16 x 16 unsigned multiply. Equation 9-1 shows the algorithm that is used. The 32-bit result is stored in four registers, RES<3:0>. EQUATION 9-1: 16 x 16 UNSIGNED MULTIPLICATION ALGORITHM EXAMPLE 9-3: 16 x 16 UNSIGNED MULTIPLY ROUTINE Example 9-4 shows the sequence to do a 16 x 16 signed multiply. Equation 9-2 shows the algorithm 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. EQUATION 9-2: 16 x 16 SIGNED MULTIPLICATION ALGORITHM EXAMPLE 9-4: 16 x 16 SIGNED MULTIPLY ROUTINE MOVF ARG1L, W MULWF ARG2L ; ARG1L * ARG2L -> ; PRODH:PRODL MOVFF PRODH, RES1 ; MOVFF PRODL, RES0 ; ; MOVF ARG1H, W MULWF ARG2H ; ARG1H * ARG2H -> ; PRODH:PRODL MOVFF PRODH, RES3 ; MOVFF PRODL, RES2 ; ; MOVF ARG1L, W MULWF ARG2H ; ARG1L * ARG2H -> ; PRODH:PRODL MOVF PRODL, W ; ADDWF RES1, F ; Add cross MOVF PRODH, W ; products ADDWFC RES2, F ; CLRF WREG ; ADDWFC RES3, F ; ; MOVF ARG1H, W ; MULWF ARG2L ; ARG1H * ARG2L -> ; PRODH:PRODL MOVF PRODL, W ; ADDWF RES1, F ; Add cross MOVF PRODH, W ; products ADDWFC RES2, F ; CLRF WREG ; ADDWFC RES3, F ; RES<3:0> = ARG1H:ARG1L ARG2H:ARG2L = (ARG1H ARG2H 216) + (ARG1H ARG2L 28) + (ARG1L ARG2H 28) + (ARG1L ARG2L) MOVF ARG1L, W MULWF ARG2L ; ARG1L * ARG2L -> ; PRODH:PRODL MOVFF PRODH, RES1 ; MOVFF PRODL, RES0 ; ; MOVF ARG1H, W MULWF ARG2H ; ARG1H * ARG2H -> ; PRODH:PRODL MOVFF PRODH, RES3 ; MOVFF PRODL, RES2 ; ; MOVF ARG1L,W MULWF ARG2H ; ARG1L * ARG2H -> ; PRODH:PRODL MOVF PRODL, W ; ADDWF RES1, F ; Add cross MOVF PRODH, W ; products ADDWFC RES2, F ; CLRF WREG ; ADDWFC RES3, F ; ; MOVF ARG1H, W ; MULWF ARG2L ; ARG1H * ARG2L -> ; PRODH:PRODL MOVF PRODL, W ; ADDWF RES1, F ; Add cross MOVF PRODH, W ; products ADDWFC RES2, F ; CLRF WREG ; ADDWFC RES3, F ; ; BTFSS ARG2H, 7 ; ARG2H:ARG2L neg? BRA SIGN_ARG1 ; no, check ARG1 MOVF ARG1L, W ; SUBWF RES2 ; MOVF ARG1H, W ; SUBWFB RES3 ; SIGN_ARG1 BTFSS ARG1H, 7 ; ARG1H:ARG1L neg? BRA CONT_CODE ; no, done MOVF ARG2L, W ; SUBWF RES2 ; MOVF ARG2H, W ; SUBWFB RES3 ; CONT_CODE : RES<3:0> = ARG1H:ARG1L ARG2H:ARG2L = (ARG1H ARG2H 216) + (ARG1H ARG2L 28) + (ARG1L ARG2H ² 28) + (ARG1L ARG2L)+ (-1 ARG2H<7> ARG1H:ARG1L 216) + (-1 ARG1H<7> ARG2H:ARG2L 216) |
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