jckarter

everyone already knows i'm a dog

the swift programming language is my fault to some degree. mostly here to see dogs, shitpost, fix old computers, and/or talk about math and weird computer programming things. for effortposts check the #longpost pinned tag. asks are open.


email
mailto:joe@duriansoftware.com
discord
jckarter
You must log in to comment.

in reply to @vaporware's post:

If this is the right motherboard:

https://commons.wikimedia.org/wiki/File:Casio-Loopy-Motherboard-FL.jpg

then it looks like the HN62434FA chip in the lower right corner of the pic is the mask ROM. If you can desolder that then you might be able to find a ROM dumper matching that kind of ROM that can work off the shelf. Otherwise, you could find a datasheet to get a pinout for the ROM, and wire it up to something with GPIO pins like a raspberry pi and dump it that way.

Ah, I guess I assumed chips from 1995 would still be too old to have any onboard PROM. But yeah, if you can find a datasheet for the CPU, hopefully there's a section about programming the ROM that should give you a lead on how to read it out.

If the ROM is mapped into the processor's address space during game execution, and the cartridge interface is known well enough to make a little cartridge of your own with a program that reads the CPU ROM out and sends it over a serial interface or something like that, that could be a straightforward way to extract it that doesn't require hacking away at the motherboard.

i was able to find a datasheet for the SH7021 on alldatasheet. it looks like it conveniently has a "PROM mode" where you can put the CPU on an adapter board and then use it like a standard EPROM in a regular EPROM dumper/programmer. so that might be one way to extract it:

instructions for putting an SH7021 cpu in PROM mode for programming

pinout mapping for adapting an SH7021 cpu to an HN27C101-style eprom

oh shoot, I'm wondering it would actually be that easy? like would they disable that somehow?

Totally worth a shot though!!! Once I get my loopy and the confidence to try this I'm going to go for it! I guess I also need a PROM reader/figure out how to make a raspberry pi do it. probs shouldn't be too hard at all.

Thanks so much! You've been more helpful than i could have imagined!