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.
「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.