Moero!! Pro Tennis (JALECO JF-17)
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Moero!! Pro Tennis (JALECO JF-17)
Hi,
Decided to leave here traces on a small project of studying the NEC D7756C sound chip, which is interesting only to two people - me and NewRisingSun
We can't get a word from Sean Riddle (hello?), so I decided to get another chip.
Turns out that it's pretty easy to do, the chip is now in processing.
In the meantime, pics of the cartridge.
Decided to leave here traces on a small project of studying the NEC D7756C sound chip, which is interesting only to two people - me and NewRisingSun
We can't get a word from Sean Riddle (hello?), so I decided to get another chip.
Turns out that it's pretty easy to do, the chip is now in processing.
In the meantime, pics of the cartridge.
Re: Moero!! Pro Tennis (JALECO JF-17)
Also attaching the current progress of the 7756 topology reconstruction.
Re: Moero!! Pro Tennis (JALECO JF-17)
I'll be interested to see how these mask-programmed ones compare to the UVEPROM one ( https://siliconpr0n.org/map/nec/d7759c/ )
Re: Moero!! Pro Tennis (JALECO JF-17)
Sean Riddle has publicly available pics of the 7756 chip, but the quality of the metal photos there is not enough for the reverse (defocus. Sean tried to focus on both the metal and the structures underneath it - it ended up being neither). The delayer photos are excellent, no complaints.
https://seanriddle.com/d7756/
So I want to take more pics of the top layer, with a good focus on the metal.
Unfortunately, it is not possible to make out the contents of the ROM and the core(?) decoder inside the chip, because ion implantation is used there. I have not yet learned how to do chemical magic to "exhibit" the N/P areas. So the research goals are to see if it is possible to access the ROM via undocumented ways. So far, I've found that the IX pads are bidirectional. This is encouraging.
https://seanriddle.com/d7756/
So I want to take more pics of the top layer, with a good focus on the metal.
Unfortunately, it is not possible to make out the contents of the ROM and the core(?) decoder inside the chip, because ion implantation is used there. I have not yet learned how to do chemical magic to "exhibit" the N/P areas. So the research goals are to see if it is possible to access the ROM via undocumented ways. So far, I've found that the IX pads are bidirectional. This is encouraging.
- rainwarrior
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Re: Moero!! Pro Tennis (JALECO JF-17)
Even if we can't read the ROM directly, if enough of the internal logic is worked out to know the sample data format and how it's output, the data could probably be estimated with fairly high confidence based on audio recordings of the samples.
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Re: Moero!! Pro Tennis (JALECO JF-17)
I see no value in doing that. If we want to use recordings, we can just use the .WAV files we have, without reencoding the sample ROM, a task that will probably demand much more guesswork and assumptions than might be initially obvious. I am thinking of things like proper audio level, or initial and trailing silence. The sample data format also is not unambiguous; some sequences of audio data have more than one valid encoding, sometimes even of the same size.
The sample data format is entirely known from MAME's µPD7559 decoder, a chip that uses a chip-external sample ROM. NEC's development flowchart indicates that a µPD7759 can be used to test the same sample ROM data that will later be embedded in a mask-ROM µPD7756C. This means that the µPD7756C must use the same sample data format and decoding logic as the µPD7759, and that MAME's µPD775689 decoder tells us everything we need to know about those aspects.
The sample data format is entirely known from MAME's µPD7559 decoder, a chip that uses a chip-external sample ROM. NEC's development flowchart indicates that a µPD7759 can be used to test the same sample ROM data that will later be embedded in a mask-ROM µPD7756C. This means that the µPD7756C must use the same sample data format and decoding logic as the µPD7759, and that MAME's µPD775689 decoder tells us everything we need to know about those aspects.
Last edited by NewRisingSun on Tue Oct 25, 2022 3:05 pm, edited 1 time in total.
- rainwarrior
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Re: Moero!! Pro Tennis (JALECO JF-17)
I do. With no sample data available, there is nothing to emulate. With estimated sample data, the emulation could be written and ready, all the issues of storage etc. can be worked out and tested. When (or if) known perfect sample data ever appears, it can simply be dropped into place.
In a similar vein, VRC7 was certainly worth emulating in the decades we had to wait before we had Nukeykt's instrument dumps.
I didn't realize we already had this. Thanks for the info.NewRisingSun wrote: ↑Tue Oct 25, 2022 2:48 pmThe sample data format is entirely known from MAME's µPD7559 decoder, a chip that uses a chip-external sample ROM.
Re: Moero!! Pro Tennis (JALECO JF-17)
Speech analysis (in that pic)? Was that actually used somewhere, and did it actually work acceptably?
Re: Moero!! Pro Tennis (JALECO JF-17)
It's just marketing. The µPD775[5-9] chips are ADPCM with your choice of sample rate. (The flowchart is literally "make sure the recording sounds good after linear ADC, then sounds good after ADPCM encoding")
- rainwarrior
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Re: Moero!! Pro Tennis (JALECO JF-17)
They were primarily used for speech sounds in these games, after all.
Re: Moero!! Pro Tennis (JALECO JF-17)
Oh, Engrish. I thought it was an actual speech-to-text chip, since the Famicom did have a mic.
Re: Moero!! Pro Tennis (JALECO JF-17)
Preliminary results of the D7756 chip in Moero Pro Tennis.
It looks like I got the very first revision (1983). The chip crumbles before my eyes after opening it.
Also the ROM area looks very suspicious to me. Whether it's the metal crumbling, or something else (EEPROM?). I'll try to clean as neatly as possible and take pictures of everything before polishing.
It looks like I got the very first revision (1983). The chip crumbles before my eyes after opening it.
Also the ROM area looks very suspicious to me. Whether it's the metal crumbling, or something else (EEPROM?). I'll try to clean as neatly as possible and take pictures of everything before polishing.