Registers

Old3DS	Name	Address	Width	Used by
Yes	PDN_CNT	0x10141000	2	Kernel11, TwlBg
Yes	PDN_WAKE_ENABLE	0x10141008	4	PTM Services, PDN Services
Yes	PDN_WAKE_REASON	0x1014100C	4	PTM Services, TwlBg, PDN Services
Yes	LGY_MODE	0x10141100	2	TwlProcess9, TwlBg
Yes	LGY_SLEEP	0x10141104	2	TwlBg
Yes	LGY_IRQ_?	0x10141108	2	TwlBg
Yes	LGY_PADCNT	0x1014110A	2	TwlBg
Yes	PDN_WIFI_UNK	0x1014110C	1	NWM Services
Yes	PDN_TWLAGB_HIDEMU_MASK	0x10141110	2	TwlBg
Yes	PDN_TWLAGB_HIDEMU_PAD	0x10141112	2	TwlBg
Yes	PDN_CODEC_0	0x10141114	2	Codec Services, TwlBg
Yes	PDN_CODEC_1	0x10141116	2	Codec Services, TwlBg
Yes	?	0x10141118	1	TwlBg
Yes	?	0x10141119	1	TwlBg
Yes	?	0x10141120	1	TwlBg
Yes	PDN_GPU_CNT	0x10141200	4	Boot11, Kernel11, PDN Services, TwlBg
Yes	PDN_VRAM_CNT	0x10141204	4	Boot11, Kernel11, TwlBg
Yes	PDN_FCRAM_CNT	0x10141210	2	Kernel11, TwlBg
Yes	PDN_CODEC_CNT	0x10141220	1	Boot11, TwlBg, PDN Services
Yes	PDN_CAMERA_CNT	0x10141224	1	PDN Services
Yes	PDN_DSP_CNT	0x10141230	1	Process9, PDN Services
No	PDN_MPCORE_CLKCNT	0x10141300	2	NewKernel11
No	PDN_MPCORE_CNT	0x10141304	2	NewKernel11
No	PDN_MPCORE_BOOTCNT<0-3>	0x10141310	1*4	NewKernel11

PDN_CNT

Bits	Description
0	1 = Enter sleep mode
2-14	Unused.
15	1 = VRAM is in self-refresh mode

Kernel11 puts VRAM in self-refresh mode (before going to sleep) by first disabling the 8 banks using GX register 0x10400030, then by disabling the GPU clock using PDN_GPU_CNT bit 16 and finally polls this register.

PDN_WAKE_ENABLE

Bits	Description
1	HID_PADCNT
3	Shell opened
4	Headphones not plugged in
8	WiFi (?)
19	Shell GPIO (?)
26	MCU interrupt
30	Touch screen pressed
31	CTR gamecard inserted/removed

List in progress.

This is a OR list of wake triggers that will wake up the console from sleep and raise IRQ 0x58.

PDN_WAKE_REASON

Same layout as PDN_WAKE_ENABLE.

This is a OR list of the wake triggers that actually woke up the console.

For each bit, write 1 to acknowledge, read, then write 0 to clear.

PDN_WIFICNT

Old3DS	Bits	Description
Yes	0	Enable wifi subsystem

LGY_MODE

Bits	Description
0-1	Read only legacy mode set on reg 0x10018000.
2-14	Unused.
15	1 = enable legacy mode.

To boot into DSi or GBA mode first set register 0x10018000 to the desired mode and setup LgyFb. Then disable FCRAM by clearing bit 0 in reg 0x10201000, writing 0 to PDN_FCRAM_CNT followed by 1 and waiting for bit 2 to clear.

The very last 3DS-mode register poke the TWL_FIRM Process9 does before it gets switched into TWL-mode, is writing 0x8000 to this register. Before writing this register, TWL Process9 waits for ARM7 to change the value of this register. The Process9 code for this runs from ITCM, since switching into TWL-mode includes remapping all ARM9 physical memory.

LGY_SLEEP

Bits	Description
0	Write 1 to wakeup GBA mode.
1	Sleep state/ack. 1 when GBA mode entered sleep. Write 1 to ack.
2	?
3-14	Unused.
15	1 = IRQ enable (IRQ 0x59)

When a GBA game enters sleep mode and bit 15 is 1, IRQ 0x59 fires and bit 1 is set. Bit 1 must be acknowledged/written together with bit 0 otherwise GBA mode wakes up from sleep early sometimes.

LGY_IRQ_?

Bitfield.

LGY_PADCNT

Also named "KEYCNT" on certain other DS(i)/GBA documentations. The value of this register is copied to HID_PADCNT when GBA mode enters sleep.

PDN_WIFIUNK

Old3DS	Bits	Description
Yes	4	Wifi-related? Set to 1 very early in NWM-module.

PDN_TWLAGB_HIDEMU_MASK

Set bits will use the corresponding values from PDN_TWLAGB_HIDEMU_PAD instead of allowing the hardware to read it from HID_PAD.

This is set to 0x1FFF (all buttons and the debug key) and PDN_TWLAGB_HIDEMU_PAD is set to 0 when the "Close this software and return to HOME Menu?" dialog is shown to prevent the button presses from propagating to the DS/GBA CPU.

PDN_TWLAGB_HIDEMU_PAD

Works the same way as HID_PAD, but the values set here are only replaced in the HID_PAD seen by the DS/GBA CPU when the corresponding bits in PDN_TWLAGB_HIDEMU_MASK are set.

PDN_GPU_CNT

Bits	Description
0	Unknown reset. 0 = reset.
1	PSC block reset? 0 = reset.
2	Geoshader block reset? 0 = reset.
3	Rasterization block reset? 0 = reset.
4	PPF block reset. 0 = reset.
5	PDC block reset? 0 = reset.
6	PDC related reset. 0 = reset.
7-15	Unused.
16	Clock enable for all blocks. 1 = enable.

Bit0: main (?) nRESET (active low), unset to reset (when not on reset, external GPU registers at 0x10400000+ are enabled). When this is unset VRAM is not accessible and triggers exceptions.

PDN uses a 12 ARM11 cycle delay to deassert reset.

PDN_VRAM_CNT

Bit0: Enable VRAM clock in older models??

This registers seems to be unimplemented in released models: while it is used in tandem with PDN_GPU_CNT.bit16 in boot11 screeninit code, Kernel11 only uses PDN_GPU_CNT.bit16 to put VRAM in self-refresh mode.

PDN_FCRAM_CNT

Bits	Description
0	Reset. 0 = reset.
1	Clock. 1 = enable, 0 = disable
2	Acknowledge clock request. Gets set or unset when toggling bit 1.

Twl-/AgbBg use this to disable FCRAM for the GBA rom in GBA mode or DSi main RAM in DSi mode. Agb-/TwlBg clears bit 0 in reg 0x10201000 before touching this reg.

Kernel11 uses it before going to sleep. It does a dummy read before touching this reg.

PDN_CODEC

The following is the only time the ARM11 CODEC module uses any 0x1EC41XXX registers. In one case CODEC module clears bit1 in register 0x1EC41114, in the other case CODEC module sets bit1 in registers 0x1EC41114 and 0x1EC41116.

PDN_CODEC_CNT

This is the power register used for the PDN CODEC service.

bit0 = unknown, bit1 = turn on/off DSP, rest = always 0.

PDN_CAMERA_CNT

This is the power register used for the PDN camera service.

bit0 = unknown, bit1 = turn on/off cameras, rest = always 0.

PDN_DSP_CNT

This is the power register used for the PDN Services DSP service.

bit0: NRESET (active low). Unset to reset/hold reset. bit1: enable bit.

PDN services holds reset for 0x30 Arm11 cycles.

PDN Registers

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