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 Post subject: MMC2 Glitches
PostPosted: Fri Sep 18, 2015 6:56 am 
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Joined: Mon Jun 09, 2014 5:10 am
Posts: 13
Hello,

I am working on a MMC2 mapper for my emulator and I am getting some strange glitches that I've spent quite a while trying to figure out.I have been through the wiki page on MMC2 with a fine tooth comb and I think I've implemented everything as it states.

Here are some screenshots for Mike Tyson's Punch Out.

When the first screen comes up all is well:
Image

Problems start happening here on the title page:
Image

It gets worse when the game actually starts as half the ring is missing (which causes the game to crash, probably because sprite zero is not hitting)
Image

The two things I have been focusing on are the bank switching in the mapper itself and also making sure that the tile byte fetches in the PPU are happening at the right pixels. As far as I can tell there isn't anything wrong with those things.

I've had a look at similar threads about MMC2 from the past but I haven't come across anyone with this particular problem. If anyone has any ideas it would be much appreciated.


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 Post subject: Re: MMC2 Glitches
PostPosted: Fri Sep 18, 2015 9:47 am 
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Joined: Fri Nov 19, 2004 7:35 pm
Posts: 3968
Looks like the game is running with horizontal mirroring, and not changing between horizontal and vertical mirroring.

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 Post subject: Re: MMC2 Glitches
PostPosted: Fri Sep 18, 2015 10:18 am 
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Joined: Mon Jun 09, 2014 5:10 am
Posts: 13
D'oh!

Thanks that was it! All working fine now :D


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