Sharp C1 cannot use expansion audio?

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NewRisingSun
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Sharp C1 cannot use expansion audio?

Post by NewRisingSun »

As I am gathering Namco 163 cartridges for my expansion audio level measurement, I noticed that every single one of them mentions that it cannot be used with the Sharp C1. None of these games use the color deemphasis bits, to my knowledge, so I wondered what the reason would be. Then I looked at the Japanese Wikipedia page on the Sharp C1, which stated:

「ワギャンランド」などの後期に出されたナムコの作品や「燃えろ!!プロ野球」など、一部遊べないゲームが存在する。カセットが差し込まれているかの判定に、音声用の信号線を使用しているためである。拡張音声が使われているゲームでは、ソフトが差し込まれていないと判定され遊ぶことができない。イジェクトスイッチはない。前面からカセットを差し込む構造上、ディスクシステムやデータックは使用できない。

Machine translation:
There are some games that can not be played, such as Namco's work in the late stage such as "Wagan Land" and "Burning !! Professional Baseball". This is because a signal line for voice is used to judge whether a cassette is inserted. In a game where extended sound is used, it is determined that software is not plugged in and it can not play.

As I understand the machine translation, the Sharp C1 somehow uses the audio in and out pins to determine whether a cartridge is plugged in, and apparently the expansion audio interferes with this somehow. (The part about Wagyan Land must be a mistake however, as Wagyan Land does not have expansion audio.)

I had not read about this before at all.
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Re: Sharp C1 cannot use expansion audio?

Post by tepples »

Two guesses:
  1. N163 games might be wired for sound mixing even if the game doesn't use it.
  2. The deck also uses VRAM /CE out, like some of the OneBus famiclones do.
Do other games using cart nametable memory have this notice, such as Napoleon Senki and After Burner?
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nothingtosay
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Re: Sharp C1 cannot use expansion audio?

Post by nothingtosay »

I can't offer any insight myself, but this surprises me because Namco composer Hiroyuki Kawada said on Twitter that the company used C1s for Famicom development. Guess those who were working on expansion audio games must have used different hardware.
NewRisingSun
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Re: Sharp C1 cannot use expansion audio?

Post by NewRisingSun »

I do not have the manuals for all these carts, but the manual for megami tensei 2 has C1 screenshots, while the Youkai Douchuuki manual obviously has composite screenshots, both in color.

I also don't quite understand why the C1 would would need to specifically detect whether a cartridge is inserted or not. But I suppose Namco eventually figured out how to bridge that circuit in order to use it for development, or they just used a devboard without expansion audio.
Great Hierophant
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Re: Sharp C1 cannot use expansion audio?

Post by Great Hierophant »

I find it curious that the article mentions "Burning !! Professional Baseball", a.k.a. Moero!! Pro Yakyuu, which is a Jaleco game from 1987. That game bridges CIRAM /CE & PPU /A13 like most games do.

The NES CartDB does show that some Namco 163 games that use do not use the expansion audio bridge the audio pins (Dragon Ninja) and some do not (Dokuganryuu Masamune)

Would this issue cause any of these games not to work in a NES with a Fami-to-NES converter?
lidnariq
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Re: Sharp C1 cannot use expansion audio?

Post by lidnariq »

I assume the C1 automatically boots the cart and switches from TV mode to Famicom mode when a cartridge is inserted... or perhaps doesn't allow you to switch to the Famicom when there's no cart.

I don't see any reason to think the presence/absence of a short between those pins would cause a problem with anything other than the C1.
kmg
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Re: Sharp C1 cannot use expansion audio?

Post by kmg »

lidnariq wrote: Mon Jan 15, 2018 12:50 pm I assume the C1 automatically boots the cart and switches from TV mode to Famicom mode when a cartridge is inserted... or perhaps doesn't allow you to switch to the Famicom when there's no cart.
There's a "TV/Canvas/Game" button on the front that cycles through TV, builtin ROM, and cart in order, presumably resetting the Famicom as necessary. I don't know if it skips the cart when the slot is empty.

Does anybody have any more info on the C1 these days? The best PCB shots I could find are in this short Japanese blog: https://bakutendo.net/blog-entry-109.html. Oh, and Enri's notes say the thing can't do 4-screen nametables, so there's that too.
Pokun
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Re: Sharp C1 cannot use expansion audio?

Post by Pokun »

Well, if there is a built-in ROM that might be why it needs to detect if something is in the cartridge slot.

The machine translation looks quite accurate to me, but it cuts out the last part that says that there is no EJECT switch and that since cartridges are plugged in from the front, the Disk System and Datach can't be used either.
Controllers and cartridge slot.
Controllers and cartridge slot.
From what I can tell from pictures there is an edge above the slot so that the Disk System would definitely not fit (besides it uses expansion audio).


Regarding Wagan Land, technically it says that "among late Namco games such as Wagan Land and Moero Pro Yakyuu there are a number of games that can't be played", so those two games are not necessarily part of the incompatible games. At least that's how I interpret it.
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TmEE
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Re: Sharp C1 cannot use expansion audio?

Post by TmEE »

The translation in first post makes me think that the audio loopback pins on cartslot are used to connect the detection signal instead of audio and vast majority of games have these two pins connected, making it a good candidate for such a use case. The few with expansion audio will fail and I suppose it was deemed small enough price to play. Of course I have not seen schematics or anything of the hardware to know for sure...
kmg
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Re: Sharp C1 cannot use expansion audio?

Post by kmg »

Pokun wrote: Mon Sep 05, 2022 3:39 pm Well, if there is a built-in ROM that might be why it needs to detect if something is in the cartridge slot.
The builtin Canvas is always loaded as the next mode after TV mode, regardless of the presence of a cart though. I'm guessing if the cart detection by audio pin thing bears out that it's just a convenience to skip over the empty cart slot and not have the customer press the TV/Canvas/Game button an extra time. When the cart is present, it's loaded with an extra button press, after the Canvas mode.
Regarding Wagan Land, technically it says that "among late Namco games such as Wagan Land and Moero Pro Yakyuu there are a number of games that can't be played", so those two games are not necessarily part of the incompatible games. At least that's how I interpret it.
The Japanese is definitely saying those are among the examples of incompatible games, i.e. something like "Moero Pro Yakyuu and later Namco games like Wagyan Land won't work". Anyway, we know this is the case, because those cartridges say they don't work with the Sharp C1 on the back. In fact a bunch of later Namco carts have that on them, which is where that wiki statement must have started :)
Pokun
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Re: Sharp C1 cannot use expansion audio?

Post by Pokun »

Oh I see, so it's just part of the mode cycle button.

You are right I see now that I interpreted it incorrectly, nado is what's marking the games as part of a non-exhaustive list of examples.
I guess Namco just marked all their later games as incompatible regardless if they used expansion audio or not.

I don't think Sharp really thought that they were sacrificing expansion audio, the C1 was released very early in the Famicom's life, before the Disk System and any game using expansion audio AFAIK, so there were probably no incompatible cartridges at the time of release.
kmg
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Re: Sharp C1 cannot use expansion audio?

Post by kmg »

Pokun wrote: Wed Sep 07, 2022 7:51 am I don't think Sharp really thought that they were sacrificing expansion audio, the C1 was released very early in the Famicom's life, before the Disk System and any game using expansion audio AFAIK, so there were probably no incompatible cartridges at the time of release.
Right, the FDS didn't come out until '86. Japanese sources say the C1 came out in '83, so maybe end of year or something? Does anybody know how long they were in production? Did they stop making these by the time the FDS went to market?

Another interesting thing about the '83 release date for the C1 would mean that it was the first thing released with an RGB PPU before the early VS. games.
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aquasnake
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Re: Sharp C1 cannot use expansion audio?

Post by aquasnake »

It is determined whether a cart is inserted by detecting the voltage difference between the audio input and audio output pins. But this destroys the compatibility of the special mapper with built-in expantion audio.

If it is to be perfectly realized, the detection should only be completed at the moment of power on reset. As an strap pin function, it cannot be detected all the time
Last edited by aquasnake on Sun Sep 11, 2022 6:17 pm, edited 1 time in total.
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aquasnake
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Re: Sharp C1 cannot use expansion audio?

Post by aquasnake »

Some famiclones (like VT console) use ciram /CE and PPU /A13 to detect whether they should boot with the built-in mapper #256 or start with an external cart
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