Subject: Re: [stella] Very BASIC ASM Info needed... From: "Andrew Davie" <adavie@xxxxxxxxxxxxx> Date: Wed, 7 Mar 2001 22:25:16 +1100 |
> Can someone please find _and_ explain it to me? :-) Well, this isn't an eor-trick. But fairly efficient. Depends on what's your poison... code size or speed. ldy FrameCounter lda NextFrame,y sta FrameCounter NextFrame .byte 1,2,0 That's just about the quickest I know... 10 cycles It also uses 10 bytes. How about this one.... lda FrameCounter cmp #2 adc #1 and #3 sta FrameCounter That's pretty cool! If the number is < 2 (ie 0 or 1) it will clear the carry, and just add 1. If its >=2 (ie: 2) it will set the carry, therefore adding two - taking it to 4 The and with 3 will then restore that to 0 Not better than the first version, though. This one is 12 cycles and 10 bytes. Still, fun :) -- _ _ _| _ _ _| _ * _ _ , (_|| )(_|( (/_\/\/ (_|(_|\/(_(/_ ,~' L_|\ ,-' \ see my Museum of Soviet Calculators at ( \ http://www.taswegian.com/MOSCOW/soviet.html \ __ / L,~' "\__/ @--> v ----- Original Message ----- From: "Manuel Polik" <manuel.polik@xxxxxxxxxxx> To: <stella@xxxxxxxxxxx> Sent: Wednesday, March 07, 2001 10:02 PM Subject: [stella] Very BASIC ASM Info needed... > Mornin' > > Supposed I want to have a counter which does 0/1/2 and then repeats. > Straightforward everybody will come up with something like this: > > INC frameCounter > LDA frameCounter > CMP #$03 > BNE CounterOk > LDA #$00 > STA frameCounter > > Now, I'm almost 100% certain, that there must be a more elegant EOR > trick here. > > Can someone please find _and_ explain it to me? :-) > > Greetings, > Manuel > > - > Archives (includes files) at http://www.biglist.com/lists/stella/archives/ > Unsub & more at http://www.biglist.com/lists/stella/ > - Archives (includes files) at http://www.biglist.com/lists/stella/archives/ Unsub & more at http://www.biglist.com/lists/stella/
Current Thread |
---|
|
<- Previous | Index | Next -> |
---|---|---|
[stella] Very BASIC ASM Info needed, Manuel Polik | Thread | Re: [stella] Very BASIC ASM Info ne, Manuel Polik |
[stella] Very BASIC ASM Info needed, Manuel Polik | Date | Re: [stella] Very BASIC ASM Info ne, Manuel Polik |
Month |