Multiply 32 bits by 32 bits in software by http://elm-chan.org/
;-----------------------------------------------------------------------------; ; 32bit x 32bit unsigned multiply ; ; Register Variables ; Call: var1[3:0] = 32bit multiplicand ; var1[7:4] = <don't care> ; var2[3:0] = 32bit multiplier ; lc = <don't care> (high register must be allocated) ; ; Result:var1[7:0] = 64bit result of var1[3:0] * var2[3:0] ; var2[3:0] = <not changed> ; lc = 0 ; ; Size = 21 words ; Clock = 436..532 cycles (+ret) ; Stack = 0 byte mul32u: sub var17,var17 ;initialize variables sub var16,var16 ; sub var15,var15 ; sub var14,var14 ; ldi lc,33 ; lc = 33; brcc PC+5 ;---- calcurating loop add var14,var20 ; adc var15,var21 ; adc var16,var22 ; adc var17,var23 ; ror var17 ; ror var16 ; ror var15 ; ror var14 ; ror var13 ; ror var12 ; ror var11 ; ror var10 ; dec lc ;if (--lc > 0) brne PC-14 ; continue loop; ret mul32s: clr lc ; Optional fast signed helper clr var14 ; process with fast unsinged routine tst var13 brpl PC+10 inc var14 com var10 com var11 com var12 com var13 adc var10,lc adc var11,lc adc var12,lc adc var13,lc tst var21 brpl PC+10 inc var14 com var20 com var21 com var22 com var23 adc var20,lc adc var21,lc adc var22,lc adc var23,lc bst var14,0 rcall mul16u brtc PC+17 com var10 com var11 com var12 com var13 com var14 com var15 com var16 com var17 adc var10,lc adc var11,lc adc var12,lc adc var13,lc adc var14,lc adc var15,lc adc var16,lc adc var17,lc ret
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