CONFIG9 Registers

Registers

Old3DS	Name	Address	Width	Used by
Yes	CFG_SYSPROT9	0x10000000	1	Boot9
Yes	CFG_SYSPROT11	0x10000001	1	Boot9
Yes	CFG_DEBUGUNIT	0x10000004	4
Yes	CFG_CARDCONF	0x1000000C	2
Yes	CFG_DEBUGGER	0x10000010	1
Yes	?	0x10000011	1
Yes	?	0x10000012	2
Yes	?	0x10000014	2
Yes	?	0x10000020	2
Yes	?	0x10000100	2
No	CFG_EXTMEMCNT9	0x10000200	1	NewKernel9
Yes	CFG_MPCORECFG	0x10000FFC	4
Yes	CFG_BOOTENV	0x10010000	4
Yes	CFG_UNITINFO	0x10010010	1	Process9
Yes	?	0x10010014	1

CFG_SYSPROT9

Writing values to SYSPROT sets the specified bitmask. The ARM9 bootrom(+0x8000) is disabled by writing bit0. bit1 is used by NATIVE_FIRM to make sure console-unique TWL AES-keys are only set at hard-boot. It is not possible to set any other bits.

From disassembly of the New3DS process9, it appears that setting bit1 disables the 0x10012000+ region.

CFG_SYSPROT11

ARM11 bootrom (+0x8000) is disabled by writing bit0. It is not possible to set any other bits.

CFG_CARDCONF

Bit	Description
1-0	Gamecard active controller select (0=NTRCARD, 1=?, 2=CTRCARD1, 3=CTRCARD2)
8	?

Depending on the gamecard controller that has been selected, one of the following gamecard registers will become active:

• Selecting NTRCARD will activate the register space at 0x10164000.
• Selecting CTRCARD1 will activate the register space at 0x10004000.
• Selecting CTRCARD2 will activate the register space at 0x10005000.

CFG_EXTMEMCNT9

This register is presumably New3DS-only. Only bit0 is writable: 0 = disable New3DS ARM9 memory at 0x08100000 size 0x80000, 1 = enable.

This bit is set by New3DS ARM9-kernel crt0.

The data in this extended memory doesn't change when disabling the memory, then re-enabling the memory. Reading this extended memory while disabled results in zeros.

CFG_MPCORECFG

Identical to PDN_MPCORE_CFG.

CFG_BOOTENV

Initially this is value zero. NATIVE_FIRM writes value 1 here when a FIRM launch begins. The LGY FIRM writes value 3 here when handling PXI command 0x00020080(first TWL PXI command), it also writes value 7 here when handling PXI command 0x00030080(first AGB PXI command). This register can be read to determine what "mode" the system is running under: hard-boot, FIRM launch, or TWL/AGB FIRM.

0=Cold boot, 1=CTR, 3=TWL, 5=NTR, 7=AGB

It is unknown if this register controls anything.

CFG_UNITINFO

This 8-bit register is value zero for retail, non-zero for dev/debug units.

0x10010014

In the console-unique TWL key-init/etc function the ARM9 copies the u8 value from REG_UNITINFO to this register.

This is also used by TWL_FIRM Process9.