Search found 40 matches

by HastatusXXI
Wed Aug 21, 2019 2:56 pm
Forum: NESemdev
Topic: Any clue on PPU emulation?
Replies: 36
Views: 32034

Re: Any clue on PPU emulation?

It occurs to me that the text on the wiki might have misled you. Any suggestions on things we might change to help with that? Sure. This page http://wiki.nesdev.com/w/index.php/NMI (operation) is well suited to come up with an implementation for NMI, while this other http://wiki.nesdev.com/w/index....
by HastatusXXI
Mon Aug 12, 2019 10:30 am
Forum: NESemdev
Topic: Any clue on PPU emulation?
Replies: 36
Views: 32034

Re: Any clue on PPU emulation?

for NMI to occur PPU has to be in VBLANK (bit 7 of $2002 toggled) and bit 7 of $2000 must be toggled during VBLANK (i.e. 0->1, but being 1 before VBLANK starts shouldn't trigger NMI, should it? [edge-sensitivity?]). It is edge-triggered, but it's triggered on (reg2000 bitAND reg2002 bitAND 128). As...
by HastatusXXI
Mon Aug 12, 2019 8:18 am
Forum: NESemdev
Topic: Any clue on PPU emulation?
Replies: 36
Views: 32034

Re: Any clue on PPU emulation?

Usually, at least the first two frames' vblank have no /NMI because the CPU is still waiting for the PPU to stabilize before enabling NMI generation in $2000. That solves my second question, thank you! However, I still have no clue about the first. Let me clarify a little bit, since my explanation ...
by HastatusXXI
Sun Aug 11, 2019 12:34 pm
Forum: NESemdev
Topic: Any clue on PPU emulation?
Replies: 36
Views: 32034

Re: Any clue on PPU emulation?

I'm unable to get NMI working properly with Donkey Kong. When the CPU arrives at this line C7DC 8D 00 20 STA $2000 = 10 A:90 X:00 Y:00 P:A4 SP:FF PPU:208, 47 CYC:64980 bit 7 of $2000 is set to 1 and, given that this is in a frame rendering, when it reaches VBLANK this bit won't change, since it's al...
by HastatusXXI
Sun Aug 04, 2019 8:01 am
Forum: NESemdev
Topic: Nintendulator log change
Replies: 12
Views: 9467

Re: Nintendulator log change

Okay, got it. Thank you both.
by HastatusXXI
Sun Aug 04, 2019 4:10 am
Forum: NESemdev
Topic: Nintendulator log change
Replies: 12
Views: 9467

Re: Nintendulator log change

I have another question. Why is $FF value shown as in memory value after performing STA when A contains $02? I'm referring to line 8981 of http://www.qmtpro.com/~nes/misc/nestest.log C68B 8D 15 40 STA $4015 = FF A:02 X:FF Y:15 P:25 SP:FB PPU: 86,233 CYC:26520 In this case the accumulator is written ...
by HastatusXXI
Sun Aug 04, 2019 3:01 am
Forum: NESemdev
Topic: Nintendulator log change
Replies: 12
Views: 9467

Re: Nintendulator log change

1. The instruction $0C you see labelled as NOP $A9A9 is an invalid opcode, in case that's confusing you at all. It is not quite a "normal" NOP. 2. nestest.nes is mapper 0, 16KB PRG + 8KB CHR, and is thus mapped to $8000-BFFF in addressing space (i.e. 16KB). NES ROM addressing space runs from $8000-...
by HastatusXXI
Sat Aug 03, 2019 10:41 am
Forum: NESemdev
Topic: Nintendulator log change
Replies: 12
Views: 9467

Re: Nintendulator log change

I'm trying to replicate Nintendulator's log (I overlooked some details in the past and this lack of information is making progress difficult). I'm having some trouble with this instruction from nestest (line 5013 of http://www.qmtpro.com/~nes/misc/nestest.log): C6C9 0C A9 A9 *NOP $A9A9 = A9 A:55 X:0...
by HastatusXXI
Sun Jul 21, 2019 8:01 am
Forum: NESemdev
Topic: Nintendulator log change
Replies: 12
Views: 9467

Re: Nintendulator log change

Thank you very much for your answers! They were quite clarifying.
by HastatusXXI
Sat Jul 20, 2019 10:05 am
Forum: NESemdev
Topic: Nintendulator log change
Replies: 12
Views: 9467

Nintendulator log change

Hi, I was looking for a nestest log, since the one I used to test my 6502 emulator disappeared from my computer. I found it in the wiki. However, when I tested my emulator its output and the log provided in the site didn't match. That seemed strange, since I remember it worked like a charm last year...
by HastatusXXI
Sat Jul 20, 2019 4:10 am
Forum: NESemdev
Topic: Any clue on PPU emulation?
Replies: 36
Views: 32034

Re: Any clue on PPU emulation?

Hi, everyone. I'm trying to resume this project, although at a slow pace... I'm still trying to understand picture representation. I made a draft tool to represent a Donkey Kong frame from CPU and PPU dump files. Everything is drawn right expect from Mario and a flame, which look reversed on their h...
by HastatusXXI
Thu Sep 27, 2018 9:11 am
Forum: NESemdev
Topic: Any clue on PPU emulation?
Replies: 36
Views: 32034

Re: Any clue on PPU emulation?

If the last value written read or written on any PPU register ($2000-$2007 or their mirrors at $2008-$3FFF) is $A5, then reading a write-only PPU register (such as $2000) will return $A5. This behavior, which FCEUX calls "PPUGenLatch", is a result of bus capacitance within the PPU. Coincidentally, ...
by HastatusXXI
Thu Sep 27, 2018 8:37 am
Forum: NESemdev
Topic: Any clue on PPU emulation?
Replies: 36
Views: 32034

Re: Any clue on PPU emulation?

I got the value $A5 from a random CPU dump of the title screen of Donkey Kong using Nintendulator. The value I'm giving to you comes from the dump at position $2000, not from watching a breakpoint. In fact, Nintendulator only shows $FF when I trace a breakpoint at $2000. I'm puzzled.
by HastatusXXI
Wed Sep 26, 2018 12:37 pm
Forum: NESemdev
Topic: Any clue on PPU emulation?
Replies: 36
Views: 32034

Re: Any clue on PPU emulation?

I successfully rendered one frame of Donkey Kong (many things were hardcoded, such as the palettes). Now I'm trying to do it properly and, following the wiki article on PPU registers, I check PPUCTRL via the CPU dump at $2000 (I know that't not the way to do it, it's temporary). I found the value $A...
by HastatusXXI
Tue Sep 25, 2018 1:41 am
Forum: NESemdev
Topic: Any clue on PPU emulation?
Replies: 36
Views: 32034

Re: Any clue on PPU emulation?

Hello again, I'm making some progress here with the PPU. I'm using Nintendulator PPU and CPU memory maps dumps to comprehend image generation. I understand backgrounds now, but I need OAM dumps to practise everything concerning sprites. Is there any possibility to do this in Nintendulator? (I only ...