Build tool/BIOSReleaseEvent - Revision history

Aoineko at 09:52, 1 May 2026

2026-05-01T09:52:19Z

2026-04-26T09:25:33Z

2026-04-26T09:24:11Z

2026-04-26T09:23:24Z

2026-04-23T20:15:58Z

2026-04-23T20:13:14Z

‎Call context

2026-04-23T20:12:53Z

‎ROM in page 0

2026-04-23T20:10:19Z

‎Usage

2026-04-19T11:07:13Z

2026-04-19T11:06:59Z

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 === RAM in page 0 ===
 * Pages 1 and 2 of memory point to the program in ROM
-* The mapper has been initialized (see [[Create_a_mapped_ROM#Initial_slot_configuration|Initial slot configuration]])
+* The mapper has not yet been initialized;
-* The global variables have been initialized (so they have their predefined values)
+** the selected segments are those selected by default by the hardware at the physical level (see https://www.msx.org/wiki/MegaROM_Mappers);
 * The <tt>main()</tt> function has not yet been called (so no program-specific initialization has taken place yet)

@@ Line 14: / Line 14: @@
 === ROM in page 0 ===
-* The global variables have not been initialized yet (so you can't use those variables because their value is undefined and any change in the callback will be overwrite later during the boot process)
+* Only page 1 of memory space points to the program in ROM
 * The mapper has not yet been initialized;
 ** the selected segments are those selected by default by the hardware at the physical level (see https://www.msx.org/wiki/MegaROM_Mappers);
 ** mapper initialization will take place immediately after the return from the BIOS_OnRelease function and will overwrite any changes made in the callback;
-* Only page 1 of memory space points to the program in ROM
+* The global variables have not been initialized yet (so you can't use those variables because their value is undefined and any change in the callback will be overwrite later during the boot process)
 * The <tt>main()</tt> function has not yet been called (so no program-specific initialization has taken place yet)
 === RAM in page 0 ===
 * The global variables have been initialized (so they have their predefined values)
 * The <tt>main()</tt> function has not yet been called (so no program-specific initialization has taken place yet)

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 [[Build tool]] option '''BIOSReleaseEvent''' is used to add a callback function to be called just before BIOS is switched out from page 0. It allows you to have an initialization code that runs while the BIOS is still accessible at page 0. For example, to detect the presence of an MSX-Music device using the BIOS routines for cross-slot reading.
-This applies to [[target]] formats that place the ROM on page 0 (ROM_48K_ISR, ROM_64K_ISR, ROM_NEO8, and ROM_NEO16), as well as ROM formats that place RAM on page 0 (via the [[Build_tool/InstallRAMISR|InstallRAMISR]] option).
+This applies to [[target]] formats that place the '''ROM on page 0''' (ROM_48K_ISR, ROM_64K_ISR, ROM_NEO8, and ROM_NEO16), as well as ROM formats that place '''RAM on page 0''' (via the [[Build_tool/InstallRAMISR|InstallRAMISR]] option).
 == Usage ==

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 === ROM in page 0 ===
 * The global variables have not been initialized yet (so you can't use those variables because their value is undefined and any change in the callback will be overwrite later during the boot process)
 * The mapper has not yet been initialized;
 ** the selected segments are those selected by default by the hardware at the physical level (see https://www.msx.org/wiki/MegaROM_Mappers);
 ** mapper initialization will take place immediately after the return from the BIOS_OnRelease function and will overwrite any changes made in the callback;
 * Only page 1 of memory space points to the program in ROM
 === RAM in page 0 ===
 * The global variables have been initialized (so they have their predefined values)
 * The mapper has been initialized (see [[Create_a_mapped_ROM#Initial_slot_configuration|Initial slot configuration]])
 * Pages 1 and 2 of memory point to the program in ROM
 === Notes ===

← Older revision		Revision as of 20:15, 23 April 2026
Line 35:		Line 35:

	For example, if you want to call the MSX-Music detection function from the BIOS_OnRelease() callback, placing the <tt>msx-music</tt> module first in the list ensures that it appears at the beginning of the ROM.		For example, if you want to call the MSX-Music detection function from the BIOS_OnRelease() callback, placing the <tt>msx-music</tt> module first in the list ensures that it appears at the beginning of the ROM.
		+	<syntaxhighlight lang="c">
		+	bool g_UseFM; // Used in BIOS_OnRelease (can't be initalized here)
		+
		+	//-----------------------------------------------------------------------------
		+	// Event called before BIOS is released
		+	void BIOS_OnRelease()
		+	{
		+	g_UseFM = (MSXMusic_Initialize() != MSXMUSIC_NOTFOUND);
		+	}
		+	</syntaxhighlight>

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 == Usage ==
-To use this option, the user must provide a function that will be called by the boot process just before the BIOS is removed from page 0 (to make room for the cartridge or memory).
+To use this option, you must provide a function that will be called by the boot process just before the BIOS is removed from page 0 (to make room for the cartridge or memory).
 Function prototype:

@@ Line 9: / Line 9: @@
 <syntaxhighlight lang="c">void BIOS_OnRelease();</syntaxhighlight>
-== Call Context ==
+== Call context ==
 You must be fully aware of the program's initialization context at the time the BIOS_OnRelease callback function is executed. This context depends on the type of target format.
@@ Line 20: / Line 20: @@
 ** mapper initialization will take place immediately after the return from the BIOS_OnRelease function and will overwrite any changes made in the callback;
 * Only page 1 of memory space points to the program in ROM
 === RAM in page 0 ===
@@ Line 26: / Line 27: @@
 * The mapper has been initialized (see [[Create_a_mapped_ROM#Initial_slot_configuration|Initial slot configuration]])
 * Pages 1 and 2 of memory point to the program in ROM