;firstname.lastname@example.org ;signed multiply of a2:a1 with b2:b1 leaving result in res4:res3:res2:res1 ; These 8 variables need to be defined, as does neg_flag ; ; Program length 64 lines ; time 134 to 248 cycles ; This program looks at the lsb of a1 to decide whether to add b1 to res2 ; ; and b2 to res3, with appropriate carrys ; It then looks at the lsb of a2 to decide whether to add b1 to res3 and ; b2 to res4, again with appropriate carrys. ; The rotates then only have to be done 8 times ; ; This is uses slightly more program but takes a little less time than ; a routine that performs one 16 bit addition per rotate and 16 rotates ; ; Multiple byte addition routine from Microchip AN617 ; Result registers used as loop counter from Bob Fehrenbach & Scott Dattalo ; clrf res4 clrf res3 clrf res2 movlw 0x80 movwf res1 clrf neg_flag btfss a2,7 goto a_pos comf a2,f comf a1,f incf a1,f btfsc status, zero incf a2,f incf neg_flag, f a_pos btfss b2,7 goto nextbit comf b2,f comf b1,f incf b1,f btfsc status, zero incf b2,f incf neg_flag, f nextbit rrf a2,f rrf a1,f btfss status, carry goto nobit_l movf b1,w addwf res2,f movf b2, w btfsc status, carry incfsz b2, w addwf res3, f btfsc status, carry incf res4, f bcf status, carry nobit_l btfss a1, 7 goto nobit_h movf b1,w addwf res3,f btfsc status, carry incf res4,f movf b2,w addwf res4,f nobit_h rrf res4,f rrf res3,f rrf res2,f rrf res1,f btfss status, carry goto nextbit btfss neg_flag, 0 goto no_invert comf res4,f comf res3,f comf res2,f comf res1,f incf res1,f btfsc status,zero incf res2,f btfsc status,zero incf res3,f btfsc status,zero incf res4,f no_invert
|file: /Techref/microchip/math/mul/16x16malin.htm, 2KB, , updated: 2002/10/28 10:08, local time: 2022/1/18 23:36,
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<A HREF="http://www.massmind.org/techref/microchip/math/mul/16x16malin.htm"> PIC Microcontoller Math Method Multiply 16x16 bit Signed from malin</A>
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