Programming ICs for donor cartridge

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danton21
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Joined: Tue Dec 07, 2021 1:53 pm

Programming ICs for donor cartridge

Post by danton21 »

Hi everyone!
Thanks to this forum I was able to create my first game for the NES/Famicom.
My next step is to use an old cartridge and write the PICs with the PRG and CHR hex.
The cartridge I took was a Home Alone(USA) clone (picture below).I see this one uses MMC3. I have two m28f101 eeprom that, as far as I see, are suitable as replacements.
What I'm using is just 2x16kb on PRG and 2x8kb on CHR on my game's code. I see MMC3 is perhaps an overkill for this game but is the cartridge I have for now (if you consider I should replace it please let me know).
My questions are:
1 - How to obtain the hex of the PRG and separately the CHR?
2 - Do i need to do any wiring? if so, why?
3 - Any detail to consider? I've read while searching for this on other posts about the iNes headers as example.

I do not pretend to get a detailed tutorial on how to do it, I'm looking for direction. Any help will be appreciated, thanks a lot!
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calima
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Re: Programming ICs for donor cartridge

Post by calima »

Your game will not run on a MMC3 cart unless the code was written for MMC3.

You will save yourself some headache by using a simple repro board like Retrostage's.
edit: Or if famicom is required, looks like Muramasa sells fc boards: https://www.muramasaentertainment.com/p ... sic-black/
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Memblers
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Re: Programming ICs for donor cartridge

Post by Memblers »

1. Try google search for "NES ROM splitter", there are several. I used to use one called ucon64 (did many other things too), if you want a command-line tool. I usually just have my assembler create the PRG file, then I add the NES header afterwards. Or for existing ROMs, I use a hex editor and cut it up by hand.

2. Pinout should be the same. I would make sure that the board has pin 31 connected to 5V, it probably does.

3. What calima said. With MMC3, you need to start in the $E000-$FFFF range, then initialize the mapper. Otherwise the PRG and CHR banks will be all wrong, nametable "mirroring" may be wrong, etc.
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