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 Post subject: Glitch in SMB
PostPosted: Thu Apr 21, 2016 2:52 pm 
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Joined: Fri Mar 18, 2016 3:59 am
Posts: 17
Hi everybody

Most parts of my FPGA NES is done. Also a couple of Test-ROMs runs very well. But in SMB i have a glitch i can't explain. Anybody seen this glitch before and can push me in the right direction? The glitch only affects the HUD when a mobile platform (like in the video) or Mario is jumping through the HUD.

http://www.boxx-it.de/~cfruth/smb_glitch/

I have another question about the DMA of the DMC audio channel. I've read that the DMA waits up to 4 cycles for memory write to end. But why? I don't understand the waiting. Will it always wait 4 cycles? Will it wait for a cycle that want to read from memory to halt the cpu? Will the first read after a write haltet? Like a /INT-Signal waiting for the current opcode to complete? How do i have to imagine this magic is working?


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 Post subject: Re: Glitch in SMB
PostPosted: Thu Apr 21, 2016 3:11 pm 
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Formerly Fx3
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Joined: Fri Nov 12, 2004 4:59 pm
Posts: 3064
Location: Brazil
How are you handling sprite zero hits? My guess is about that. It seems you're taking the first non-transparent pixel of sprite overlapping the background. It should be the sprite 0 pixel.


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 Post subject: Re: Glitch in SMB
PostPosted: Thu Apr 21, 2016 4:12 pm 
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Joined: Sat Feb 12, 2005 9:43 pm
Posts: 10068
Location: Rio de Janeiro - Brazil
Heh, it does indeed look like any sprite is able to trigger a hit, but only sprite 0 should do it.


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 Post subject: Re: Glitch in SMB
PostPosted: Fri Apr 22, 2016 1:10 am 
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Joined: Fri Mar 18, 2016 3:59 am
Posts: 17
Hi guys

You're right. I tested for non-transparent pixel of first sprite in secondary OAM and not OAM *grmpf*
Added a flag if sprite 0 is in secondary OAM and it looks really good now. Thanx :-)


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 Post subject: Re: Glitch in SMB
PostPosted: Fri Apr 22, 2016 7:33 am 
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Joined: Sun Sep 19, 2004 11:12 pm
Posts: 19122
Location: NE Indiana, USA (NTSC)
Feuerwerk42 wrote:
Added a flag if sprite 0 is in secondary OAM

Anyone remember what that flag was called in Visual 2C02?


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 Post subject: Re: Glitch in SMB
PostPosted: Fri Apr 22, 2016 9:56 am 
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Joined: Sun Apr 13, 2008 11:12 am
Posts: 6303
Location: Seattle
Just looking through nodenames.js, read_2002_output_spr0_hit, spr0_hit, /spr0_hit, set_spr0_hit...


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 Post subject: Re: Glitch in SMB
PostPosted: Fri Apr 29, 2016 5:53 pm 
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Joined: Sun May 27, 2012 8:43 pm
Posts: 1308
This is neat! Do you have any plans on sharing your HDL work?


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 Post subject: Re: Glitch in SMB
PostPosted: Sat Apr 30, 2016 3:57 am 
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Joined: Fri Mar 18, 2016 3:59 am
Posts: 17
Hi

Sure, i will add it to my GitHub-Account. Give me some days to change the commentary
to english and add a bit more *cough*

Greetings
Chris


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