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Add MASK_EN note #629

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3edbf6b
Add MASK_EN note
dmitry-shechtman Oct 2, 2025
7f4c1a9
Fix missing container closure
dmitry-shechtman Oct 2, 2025
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7 changes: 7 additions & 0 deletions src/SGB_Command_System.md
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Expand Up @@ -24,6 +24,13 @@ after having displayed the picture). The Cancel Mask function may be
also invoked (optionally) by completion of PAL_SET and ATTR_SET
commands.

:::tip

SGB freezes/unfreezes the Game Boy screen automatically whenever the LCD is
turned off/on.
Comment on lines +29 to +30
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@ISSOtm ISSOtm Oct 4, 2025 •
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Suggested change
SGB freezes/unfreezes the Game Boy screen automatically whenever the LCD is
turned off/on.
The screen retains its last frame when the "LCD" is [turned off](<#LCDC.7 — LCD enable>), though it gets blanked out after a while.

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@dmitry-shechtman dmitry-shechtman Oct 4, 2025

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I think "stops updating" might confuse people, although it's technically correct.
I'm not sure what "gets blanked out after a while" means.

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@ISSOtm ISSOtm Oct 4, 2025

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AFAIK, leaving the screen turned off for a significant period of time causes the SGB firmware to blank out the framebuffer.

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@dmitry-shechtman dmitry-shechtman Oct 4, 2025

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@nitro2k01?

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@nitro2k01 nitro2k01 Oct 13, 2025 •
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I think there's a lot of detail that could be discovered through hardware research. Personally, I'd prefer to hold off on edits that go from saying something that's unconfirmed and maybe half correct to something else that's that's unconfirmed and maybe half correct. Especially when it comes to the SGB which is a device that both most people don't have access to, and isn't emulated 100% accurately, even in low level emulators that emulate the SNES portion of the equation.

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@pinobatch pinobatch Oct 13, 2025

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Do I need to call Cubby 🐻️ again for a test of how long it takes SGB to discard the last frame after LCD off?

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@ISSOtm ISSOtm Oct 15, 2025

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Well, then following Nitro's logic, we should not include the original claim at all either?

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@ISSOtm ISSOtm Oct 15, 2025

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Addition of that claim is tracked by #625, btw.

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@pinobatch pinobatch Nov 4, 2025

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I don't see where "it gets blanked out after a while" came from. Cubby didn't know either 🐻️

I wrote a test ROM that displays an image, turns off LCD while the A Button is held, and turns LCD back on once the A Button is released. DMG and GBC hid the image while A is held. NTSC SGB1 retained the image for my entire patience (about 20 seconds) and showed a little blip at the bottom of the play area indicating that the ICD2 was once again receiving signal from LCD out.

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@dmitry-shechtman dmitry-shechtman Nov 5, 2025

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Can we safely remove the "gets blanked out after a while" bit?


:::

## SGB Command $0C — ATRC_EN

Used to enable/disable Attraction mode, which is enabled by default.
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