Code:
; 16bit by 16bit unsigned multiply ; by Martin Sturm 2010 ; tested ; ; aH:aL * bH:bL --> r4:r3:r2:r1 ; ; t1 is a temporary variable ; if modifying a or b is ok, aL, bL, or bH can be used as t1 ; ; 140 instructions, 140 cycles ; ; helper macro mmac MACRO A,bit, u2,u1 BTFSC A,bit ADDWF u2,F RRF u2,F RRF u1,F ENDM MULT_16x16_FASTEST MACRO aH,aL, bH,bL, r4,r3,r2,r1, t1 ; 16x8 multiply aH:aL * bL -> r3:r4:r1 CLRF r3 CLRF r1 CLRC MOVFW bL mmac aL,0, r3,r1 mmac aL,1, r3,r1 mmac aL,2, r3,r1 mmac aL,3, r3,r1 mmac aL,4, r3,r1 mmac aL,5, r3,r1 mmac aL,6, r3,r1 mmac aL,7, r3,r1 CLRF r4 ; carry already clear from last RRF of mmac above ; bL still in W mmac aH,0, r3,r4 mmac aH,1, r3,r4 mmac aH,2, r3,r4 mmac aH,3, r3,r4 mmac aH,4, r3,r4 mmac aH,5, r3,r4 mmac aH,6, r3,r4 mmac aH,7, r3,r4 ; 16x8 multiply aH:aL * bH -> r4:t1:r2 ; middle byte from previous 16x8 multiplication starts in r4 ; but ends in r2 CLRF r2 MOVFW bH ; carry already clear from last RRF of mmac above mmac aL,0, r4,r2 mmac aL,1, r4,r2 mmac aL,2, r4,r2 mmac aL,3, r4,r2 mmac aL,4, r4,r2 mmac aL,5, r4,r2 mmac aL,6, r4,r2 mmac aL,7, r4,r2 ; W still holds bH CLRF t1 ; bH,bL, or aL may be used for t1 ; carry already clear from last RRF of mmac above mmac aH,0, r4,t1 mmac aH,1, r4,t1 mmac aH,2, r4,t1 mmac aH,3, r4,t1 mmac aH,4, r4,t1 mmac aH,5, r4,t1 mmac aH,6, r4,t1 mmac aH,7, r4,t1 ; add middle byte aH:aL * bH to upper byte of aH:aL * bL MOVFW t1 ADDWF r3,F SKPNC INCF r4,F ENDM
Questions:
file: /Techref/microchip/math/mul/m16x16mds.htm, 3KB, , updated: 2010/7/13 16:15, local time: 2024/10/12 02:09,
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