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PostPosted: Mon Feb 20, 2006 11:19 am 
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Test "2.details.nes" #7 indeed checks that it's decremented exactly 241, no more, no less. Here's the code for that test:

Code:
ldx   #241              ; load counter with 241
jsr   begin_counter_test
jsr   wait_vbl
lda   #0
sta   $2005
sta   $2005
lda   #$08              ; sprites use tiles at $1xxx
sta   $2000
lda   #$18              ; enable bg and sprites
sta   $2001
ldy   #25               ; 29800 delay for frame
lda   #237       
jsr   delay_ya8
lda   #$00              ; disable rendering
sta   $2001
jsr   irq_should_be_clear; counter should be at 1 now (no IRQ yet)
jsr   clock_counter
jsr   irq_should_be_set ; counter should be at 0 now (IRQ occurring)


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PostPosted: Mon Feb 20, 2006 1:39 pm 
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Great. This makes the things a bit easier. :)

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PostPosted: Tue Feb 21, 2006 11:13 pm 
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Anonymous wrote:
If sprites are set to $1000-1FFF and the background is set to $0000-0FFF, then A12 will change from 0 to 1 at cycle 260 of each scanline, then change from 1 to 0 at cycle 320 of each scanline.

If sprites are set to $0000-0FFF and the background is set to $1000-1FFF, then A12 will change from 1 to 0 at cycle 256 of each scanline, then change from 0 to 1 at cycle 324 of each scanline.

If sprites and the background are set to the same pattern table, then no decrement occurs because A12 will never be set to 0 long enough for the MMC3 to detect it.

Such is my understanding, anyway.


Are these numbers correct? I saw a "no" post immediatly afterward without quoting a specific post.
What's the scale, or what kind of cycles are these? Are these the ones that go up to 341?
What are the equivalent cycle numbers for PAL mode, if they aren't the same?

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PostPosted: Wed Feb 22, 2006 9:13 am 
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Any other mappers use the same A12 rising edge method as MMC3? (tengen rambo?)

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PostPosted: Wed Feb 22, 2006 12:34 pm 
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i see DWedit avatar... Dwedit, are you a girl or a boy???

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PostPosted: Wed Feb 22, 2006 1:09 pm 
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I honnestly not think Nesdev is a good place to get girlfirends. For a sad obscure reason, all girls aren't interested in what is interesting, and they are interested in what isn't interesting.

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PostPosted: Wed Feb 22, 2006 1:31 pm 
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Bregalad wrote:
I honnestly not think Nesdev is a good place to get girlfirends. For a sad obscure reason, all girls aren't interested in what is interesting, and they are interested in what isn't interesting.

Hahaha! My girlfriend can get really bored if I even *try* to talk about NESdev with her. She likes games though, so we can at least discuss ideas for games, but not the actual coding of them.


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 Post subject: Re: a question
PostPosted: Wed Feb 22, 2006 1:32 pm 
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lord_Chile wrote:
i see DWedit avatar... Dwedit, are you a girl or a boy???


Dwedit's name, according to http://dwedit.home.comcast.net/, is Dan Weiss, so I'll let you draw your own conclusions.

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 Post subject: Re: a question
PostPosted: Wed Feb 22, 2006 2:51 pm 
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Location: Chile (South America), Quilpué
yeah, nesdev is for nes i agree. but if i see a girl coding on nesdev i would like asking for marry hahhhahaa!

i like so much nesdev hahha.. i would be crazy!

i dont know if dan is a girl or man name, on chile it's uncommon and i dont know about it.. anyway i think he is a boy, good luck

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PostPosted: Wed Feb 22, 2006 4:23 pm 
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Dwedit wrote:
Any other mappers use the same A12 rising edge method as MMC3? (tengen rambo?)


If it's of any interest (I doubt anyone would emulate it soon), my Squeedo cart uses PPU A12. I hooked it up to clock one of the PIC's timers, set to be counted on rising edges and pre-scaled by 8, and that works.


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PostPosted: Sat Feb 25, 2006 10:15 am 
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I did a log tracing test #7 and... I must be misunderstanding something about how A12-IRQ clocking work... :(
Code:
E26A STA $2001      [A=00 X=00 Y=00 S=FD P=37] --- --- (7A)


It must be 01! :(
You see... My code checks for A12 rising edges at every single CPU clock cycle, or A12 0->1 changes (to be exact). In fact, F1h - 7Ah = 77h (119). Actually, the excessive branch loops make the log a bit huge... so, analysing it becomes harder.

Anyway, what's up?

EDIT-- nope, even using the 8 cycles "latency" between A12 rising edges, it still fails at #7. It seems 0->1 isn't the true rule after all, but A12=1 and again 1 every 8 CPU cycles?

EDIT2-- what's the actual behaviour regarding 2000h, please? bump... bump...

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PostPosted: Wed Mar 01, 2006 6:42 am 
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$2000 info: http://nesdevwiki.ath.cx/index.php/NES_PPU

And keep in mind the PPU temp address gets updated too (see Loopy's 'skinny on NES scrolling' document), in short: temp address A10, A11 = $2000 D0, D1.


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PostPosted: Wed Mar 01, 2006 2:39 pm 
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No. I mean 2000h bits stopping the MMC3 IRQ counter. ^_^;;

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PostPosted: Wed Mar 01, 2006 3:19 pm 
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Setting bits 3 and 4 of $2000 to 0 would stop the MMC3 IRQ counter during normal rendering, and that's simply because an A12 rising edge won't happen: during rendering, the PPU would read from nametables/attribute data ($2000-$2fff: A12=0), and fetch sprite AND background tiles from $0000-$0ffff (A12=0 again).

You could still manually clock the counter by eg. writing to the palette ($3fxx: A12=1).


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PostPosted: Sat Mar 04, 2006 1:08 pm 
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I give up, it simply doesn't work. :( Not unusual that MMC3 IRQs are... annoying. Even map90 was easier than this one. I might go back into old method. Damn it.

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