Multiplying using Hardware Multiplyer (AVR ASM)
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; Last change: MWL 21 Jul 99 1:34 pm ;**** A P P L I C A T I O N N O T E A V R 2 0 1 *************************** ;* ;* Title : 16bit multiply routines using hardware multiplier ;* Version : V1.0 ;* Last updated : 5 Apr, 1999 ;* Target : ATmega83/161/163 ;* ;* Support email : avr@atmel.com ;* ;* DESCRIPTION ;* This application note shows a number of examples of how to implement ;* 16bit multiplication using hardware multiplier. Refer to each of the ;* funtions headers for details. The functions included in this file ;* are : ;* ;* mul16x16_16 - Multiply of two 16bits numbers with 16bits result. ;* mul16x16_32 - Unsigned multiply of two 16bits numbers with 32bits ;* result. ;* muls16x16_32 - Signed multiply of two 16bits numbers with 32bits ;* result. ;* mac16x16_32 - Signed multiply accumulate of two 16bits numbers ;* with a 32bits result. ;* fmuls16x16_32 - Signed fractional multiply of two 16bits numbers ;* with 32bits result. ;* fmac16x16_32 - Signed fractional multiply accumulate of two 16bits ;* numbers with a 32bits result. ;* ;****************************************************************************** ;****************************************************************************** ;* ;* FUNCTION ;* mul16x16_16 ;* DECRIPTION ;* Multiply of two 16bits numbers with 16bits result. ;* USAGE ;* r17:r16 = r23:r22 * r21:r20 ;* STATISTICS ;* Cycles : 9 + ret ;* Words : 6 + ret ;* Register usage: r0, r1 and r16 to r23 (8 registers) ;* NOTE ;* Full orthogonality i.e. any register pair can be used as long as ;* the result and the two operands does not share register pairs. ;* The routine is non-destructive to the operands. ;* ;****************************************************************************** mul16x16_16: mul r22, r20 ; al * bl movw r17:r16, r1:r0 mul r23, r20 ; ah * bl add r17, r0 mul r21, r22 ; bh * al add r17, r0 ret ;****************************************************************************** ;* ;* FUNCTION ;* mul16x16_32 ;* DECRIPTION ;* Unsigned multiply of two 16bits numbers with 32bits result. ;* USAGE ;* r19:r18:r17:r16 = r23:r22 * r21:r20 ;* STATISTICS ;* Cycles : 17 + ret ;* Words : 13 + ret ;* Register usage: r0 to r2 and r16 to r23 (11 registers) ;* NOTE ;* Full orthogonality i.e. any register pair can be used as long as ;* the 32bit result and the two operands does not share register pairs. ;* The routine is non-destructive to the operands. ;* ;****************************************************************************** mul16x16_32: clr r2 mul r23, r21 ; ah * bh movw r19:r18, r1:r0 mul r22, r20 ; al * bl movw r17:r16, r1:r0 mul r23, r20 ; ah * bl add r17, r0 adc r18, r1 adc r19, r2 mul r21, r22 ; bh * al add r17, r0 adc r18, r1 adc r19, r2 ret ;****************************************************************************** ;* ;* FUNCTION ;* muls16x16_32 ;* DECRIPTION ;* Signed multiply of two 16bits numbers with 32bits result. ;* USAGE ;* r19:r18:r17:r16 = r23:r22 * r21:r20 ;* STATISTICS ;* Cycles : 19 + ret ;* Words : 15 + ret ;* Register usage: r0 to r2 and r16 to r23 (11 registers) ;* NOTE ;* The routine is non-destructive to the operands. ;* ;****************************************************************************** muls16x16_32: clr r2 muls r23, r21 ; (signed)ah * (signed)bh movw r19:r18, r1:r0 mul r22, r20 ; al * bl movw r17:r16, r1:r0 mulsu r23, r20 ; (signed)ah * bl sbc r19, r2 add r17, r0 adc r18, r1 adc r19, r2 mulsu r21, r22 ; (signed)bh * al sbc r19, r2 add r17, r0 adc r18, r1 adc r19, r2 ret ;****************************************************************************** ;* ;* FUNCTION ;* mac16x16_32 ;* DECRIPTION ;* Signed multiply accumulate of two 16bits numbers with ;* a 32bits result. ;* USAGE ;* r19:r18:r17:r16 += r23:r22 * r21:r20 ;* STATISTICS ;* Cycles : 23 + ret ;* Words : 19 + ret ;* Register usage: r0 to r2 and r16 to r23 (11 registers) ;* ;****************************************************************************** mac16x16_32: clr r2 muls r23, r21 ; (signed)ah * (signed)bh add r18, r0 adc r19, r1 mul r22, r20 ; al * bl add r16, r0 adc r17, r1 adc r18, r2 adc r19, r2 mulsu r23, r20 ; (signed)ah * bl sbc r19, r2 add r17, r0 adc r18, r1 adc r19, r2 mulsu r21, r22 ; (signed)bh * al sbc r19, r2 add r17, r0 adc r18, r1 adc r19, r2 ret mac16x16_32_method_B: ; uses two temporary registers ; (r4,r5), but reduces cycles/words ; by 1 clr r2 muls r23, r21 ; (signed)ah * (signed)bh movw r5:r4,r1:r0 mul r22, r20 ; al * bl add r16, r0 adc r17, r1 adc r18, r4 adc r19, r5 mulsu r23, r20 ; (signed)ah * bl sbc r19, r2 add r17, r0 adc r18, r1 adc r19, r2 mulsu r21, r22 ; (signed)bh * al sbc r19, r2 add r17, r0 adc r18, r1 adc r19, r2 ret ;****************************************************************************** ;* ;* FUNCTION ;* fmuls16x16_32 ;* DECRIPTION ;* Signed fractional multiply of two 16bits numbers with 32bits result. ;* USAGE ;* r19:r18:r17:r16 = ( r23:r22 * r21:r20 ) << 1 ;* STATISTICS ;* Cycles : 20 + ret ;* Words : 16 + ret ;* Register usage: r0 to r2 and r16 to r23 (11 registers) ;* NOTE ;* The routine is non-destructive to the operands. ;* ;****************************************************************************** fmuls16x16_32: clr r2 fmuls r23, r21 ; ( (signed)ah * (signed)bh ) << 1 movw r19:r18, r1:r0 fmul r22, r20 ; ( al * bl ) << 1 adc r18, r2 movw r17:r16, r1:r0 fmulsu r23, r20 ; ( (signed)ah * bl ) << 1 sbc r19, r2 add r17, r0 adc r18, r1 adc r19, r2 fmulsu r21, r22 ; ( (signed)bh * al ) << 1 sbc r19, r2 add r17, r0 adc r18, r1 adc r19, r2 ret ;****************************************************************************** ;* ;* FUNCTION ;* fmac16x16_32 ;* DECRIPTION ;* Signed fractional multiply accumulate of two 16bits numbers with ;* a 32bits result. ;* USAGE ;* r19:r18:r17:r16 += (r23:r22 * r21:r20) << 1 ;* STATISTICS ;* Cycles : 25 + ret ;* Words : 21 + ret ;* Register usage: r0 to r2 and r16 to r23 (11 registers) ;* ;****************************************************************************** fmac16x16_32: clr r2 fmuls r23, r21 ; ( (signed)ah * (signed)bh ) << 1 add r18, r0 adc r19, r1 fmul r22, r20 ; ( al * bl ) << 1 adc r18, r2 adc r19, r2 add r16, r0 adc r17, r1 adc r18, r2 adc r19, r2 fmulsu r23, r20 ; ( (signed)ah * bl ) << 1 sbc r19, r2 add r17, r0 adc r18, r1 adc r19, r2 fmulsu r21, r22 ; ( (signed)bh * al ) << 1 sbc r19, r2 add r17, r0 adc r18, r1 adc r19, r2 ret fmac16x16_32_method_B: ; uses two temporary registers ; (r4,r5), but reduces cycles/words ; by 2 clr r2 fmuls r23, r21 ; ( (signed)ah * (signed)bh ) << 1 movw r5:r4,r1:r0 fmul r22, r20 ; ( al * bl ) << 1 adc r4, r2 add r16, r0 adc r17, r1 adc r18, r4 adc r19, r5 fmulsu r23, r20 ; ( (signed)ah * bl ) << 1 sbc r19, r2 add r17, r0 adc r18, r1 adc r19, r2 fmulsu r21, r22 ; ( (signed)bh * al ) << 1 sbc r19, r2 add r17, r0 adc r18, r1 adc r19, r2 ret ;**** End of File **** |