A Moogle  🏳️‍🌈 💻 🎮 🎶 🇸🇪

@Arisotura If it's not too much trouble, may I ask a few questions related to DS behavior during cold boot? My emulated ARM7 is getting oddly chatty with the nonexistent game card, and I'm wondering if it thinks there's a game card there (and how to convince it there's not).

normally just returning blank cart data (all FF or 00) should be enough, if not you might have a CPU bug

On one hand I'm reluctant to suspect a CPU bug given that the ARM7 emulation I'm working with can handle both Linux and WinCE, but neither of those use Thumb mode. Since 0xFF is being returned for all cart data, could be a Thumb bug lurking.

It might also explain why the first time it tries to invoke halt mode, R12 has the wrong value, so it ends up trying to STRB into the firmware ROM area instead.

nah, that one also happens in melonDS, that's a bug in Nintendo's code.

Well, darn. In that case I have even less of an idea. I'm not sure how you feel about other devs using melonDS code as reference, so if it's not too much, do you know offhand (or can you confirm) whether or not the BIOS tries to initiate KEY1 mode, even with no game card?

I'm fine with melonDS code being used as a reference; infact that's also what the code is for! I don't recall details of cart comm but I don't think it should go further than trying to retrieve the cart header if there's no cart present.