I need some help with my CHR rom (NES Music Cart) (Page 1) - Nintendo Consoles - Forums

1 Nov 6, 2013 9:54 am

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Dallas, Texas

So I'm making a music cart for NES and my music is playing with no issues, but my graphics I had made for it are not showing up right. I get either black screen or some glitchy squares moving in time with the audio. Please let me know if you have a solution. Thanks.

Now I've read somewhere that using copy /b and actually merging 4 of the same 8K CHR.BINs into one larger CHR.BIN filling up the entire 32K space might work. Is that just being wateful? Should I just get some smaller chips, and are smaller sizes even compatible? I'm not to sure on the pinouts of 27C64s compared to the 256.

Last edited by TylerBarnes (Nov 6, 2013 11:12 am)

2 Nov 6, 2013 12:45 pm

HeavyW8bit

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Parts Unkown

Size of Chr chip depends on the donor cart you are using. If it's NROM then the Chr should be 8k I believe. Pinouts for 27c64 are the same as 27c256 so it should not be an issue. Hope this helps!

3 Nov 6, 2013 2:23 pm

nitro2k01

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Sweeeeeeden

I think the problem is that the PPU is reading from the wrong 8 kiB section of the CHR ROM. Filling up the ROM should solve your problem entirely.
You might also want to compare the ROM chip's pinout to the original chip's pinout and look for subtle difference. Or ask in the NESDev forums.

4 Nov 6, 2013 3:24 pm

Batsly Adams

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Brooklyn, NY

Agreeing with nitro2k01 here - use copy /b to populate the entire ROM since the two high address bits are just floating in this case. Don't worry about being wasteful, just use whatever is easily accessible / accommodates your program. Message me if you need a hand!

Also : the squares might be your OAM pointing at the music player RAM.

5 Nov 6, 2013 4:06 pm

Jazzmarazz

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Michigan

Agreeing with everyone else, fill her up. The pinout for the 28-pin CHR Mask ROm and the 27c256 is exactly the same, so it shuold be a drop-in-replacement.

CHR Mask ROM
http://nesdev.com/NES%20ROM%20Pinouts.txt

27C256
http://www.epanorama.net/images/semi/mcu/27C256.gif

I did also notice that the NROM cartridge has two jumpers labelled V and H. Is this true with yours? I do not know of the effect of using the incorrect type of mirroring, but worst case scenario, maybe? Check that lastly of course.