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 Post subject: Mapper 1 CHR issues
PostPosted: Sun Dec 16, 2018 12:58 am 
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Joined: Sat Nov 10, 2018 2:49 pm
Posts: 9
I'm starting to implement mappers into my Nes emulator and I'm using Zelda 1 to test out mapper 1 support. PRG banks are fine but CHR banks give me a lot of trouble. I got the text to load by starting CHR banks at $778f in the Rom file but everything else is still garbage and this address doesn't make sense. I tried searching the sequence of bytes for the "0" character but only one match was found.

I'm using resources from: https://wiki.nesdev.com/w/index.php/MMC1

I tried searching about this issue but I couldn't find anything.


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 Post subject: Re: Mapper 1 CHR issues
PostPosted: Sun Dec 16, 2018 4:21 am 
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Joined: Thu Sep 15, 2005 9:23 am
Posts: 1232
Location: Berlin, Germany
Zelda 1 doesn't have any CHR ROM banks. It uses CHR RAM instead.


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 Post subject: Re: Mapper 1 CHR issues
PostPosted: Sun Dec 16, 2018 9:32 am 
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Joined: Sat Feb 12, 2005 9:43 pm
Posts: 11094
Location: Rio de Janeiro - Brazil
When a game uses CHR-RAM (CHR pages specified as 0 in the iNES header), your emulator shouldn't load any CHR data automatically. Instead, give the game 8KB (or more if specified in an NES 2.0 mapper) of empty RAM in the CHR area that the game code itself will populate it with tiles.


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 Post subject: Re: Mapper 1 CHR issues
PostPosted: Sun Dec 16, 2018 2:09 pm 
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Joined: Sat Nov 10, 2018 2:49 pm
Posts: 9
Thanks for the information. It's fixed now and everything else that I need to fix for this game seems very straight forward.


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