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→TWL_FIRM and AGB_FIRM
== TWL_FIRM and AGB_FIRM ==
== TWL_FIRM and AGB_FIRM ==
TWL_FIRM handles DS(i) backwards compatibility, while AGB_FIRM handles running GBA VC titles. The ARM9 FIRM section for TWL_FIRM and AGB_FIRM are exactly the same(for TWL_FIRM and AGB_FIRM versions which were updated with the same system-update).
TWL_FIRM handles DS(i) backwards compatibility, while AGB_FIRM handles running GBA VC titles. The ARM9 FIRM section for TWL_FIRM and AGB_FIRM are exactly the same(for TWL_FIRM and AGB_FIRM versions which were updated with the same system-update).
=== TWL_FIRM ===
The 3DS-mode ARM9 core seems to switch into DSi-mode(for running DSi-mode ARM9 code) by writing to a [[PDN]] register(this changes the memory layout to DSi-mode / etc, therefore this register poke *must* be executed from ITCM). This is the final 3DS-mode register poke before the ARM9 switches into DSi-mode. It's unknown how exactly DS(i)-mode ARM7 code is run. Trying to read from the exception-vector region(address 0x0) under this DSi-mode ARM7 seems to only return 0x0 data. Also note that this DSi-mode ARM7 runs code(stored in TWL_FIRM) which pokes some DSi-mode registers that on the DSi were used for disabling access to the DSi bootROMs, however these registers do not affect the 3DS DSi-mode ARM9/ARM7 "bootrom" region(exceptionvector region + 0x8000) at all.