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FamiTracker
The famicom game [url=http://bootgod.dyndns.org:7777/profile.php?id=3953]Famicom Trainer 3: Aerobics Studio is known to have a 960B(?) PCM decoder ROM on the board. Unfortunately, not much is known about its operation. Only warehouse stock listings and a very vague NESdev thread have information on the Mitsubishi M50805 chip.
Here is a [url=http://www.youtube.com/watch?v=kgpRx_ypbxQ]video of the chip in action.
Since the internet world has little to no information, I've taken matters into my own hands.
[quote="B00daW@NESdev"]I've attempted to search for patents, contact Mitsubishi, and get a hold of the warehouse that they referred me to without any luck of finding datasheets. So, I've debugged the ROM and found out a few things:
$6000
xSxx xPPP
P = Play sample number.
S = Stop sample.
I believe there are a maximum of 8 samples. I've made it through all of the modes and realize that the max sample value before it is DEY'd is $08 (which is #$07). Also at init #$FF is written to $6000. I'm not sure of its function.[/quote]
Since it's supposedly a 960 byte (?) mask ROM chip mapped at $6000 and possibly a maximum of 8 playable samples each sample would be 120 bytes each. Now what we do not know at this moment is the encoding algorithm. I would put my money on 4-bit ADPCM to 8 or 9-bit PCM.
I've since purchased a Famicom Trainer 3: Aerobics Studio cart from Japan. When it arrives in the mail I'll use my CopyNES and its debugger function to poke around the register to see what else may happen in the bits that I do not yet understand function.
Thats really cool! Can you explain what we might be able to do with this? Would it be like DPCM but with more/better quality samples? (Stupid question lol)
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Like the other D775xx chip in Jaleco games, it could potentially be used as a no-effort PCM playback chip. This means that with addition to DPCM, more samples could be played without adding more load to the 2a0x's processing.
Are you being a cunt on purpose, or do you not know the sarcastic nature of the phrase "cool story, bro"?
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Follow me on [url=https://twitter.com/jrlepage2a03]Twitter.
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[url=http://famitracker.com/forum/posts.php?id=4081]>HERE< is where the lot of you and your topic is going. Enjoy and have a nice time.
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I'll let you guys know when the package comes in the mail and what I find out about the chip.
Most likely I'm going to have to send it somewhere to someone a lot smarter and more capable than myself to destroy it for science. Who knows? This chip may have also been used in obscure arcade cabinets or electronic devices and MAME/MESS might want the info too.
I wonder if you could make an NSF that writes to that chip's register, and if so I wonder if you could play it on the real hardware using an HFC3.
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Follow me on [url=https://twitter.com/jrlepage2a03]Twitter.
I record (some) NSFs on hardware. Feel free to [url=http://www.famitracker.com/forum/posts.php?id=3633]request a hardware render.
Totally! Could be done with FamiTone. You could make the Zxx command a direct write to the M50805.
Z40 would be sample cut off.
Z00-Z07 would be sample play. :D
Edit: On second thought, I know it's possible, but the NSF format may need to be adjusted. Luckily there are two more unused expansion bits present in NSF1. I believe 8K of RAM needs to be present between $6000-$7FFF. I'm also not entirely sure how the NSF player would work if a part of the player routine is to clear RAM writing #$00 to $6000-$7FFF. I also don't know the entire mapped area where the M50805 resides. It may be that entire area. That means when the player inits that it might play a shit-ton of samples; being that writing #$00 to $6000 will play the first sample.
Eh, the conflict is not necessarily a problem. It's the same deal with how FDS expansion enables RAM everywhere, but even less of a problem because almost nobody uses the RAM at $6000-7FFF for NSFs anyway. If Family Aerobics doesn't use the RAM then overwriting stuff in RAM when messing with the chip won't matter, and nothing will need to read it.
OK. I just needed to verify this. I didn't know if the emulated player or maybe the TNS-HFCx or NES PowerPak used that area for anything else. Good to know there is somewhat of a standard going on.
