Changes

=== TWL_FIRM ===

=== 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 0x00/0xFF 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.

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. DS(i)-mode ARM7 code is run on the internal [[ARM7]] core, which is started up during TWL_FIRM boot. Trying to read from the exception-vector region(address 0x0) under this DSi-mode ARM7 seems to only return 0x00/0xFF 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.

For shutting down the system, TWL_FIRM writes u8 value 8 to [[I2C]] MCU register 0x20. For returning to 3DS-mode, TWL_FIRM writes value 4 to that MCU register to trigger a hardware system reboot.

For shutting down the system, TWL_FIRM writes u8 value 8 to [[I2C]] MCU register 0x20. For returning to 3DS-mode, TWL_FIRM writes value 4 to that MCU register to trigger a hardware system reboot.