SPI Registers

Registers

Old3DS	Name	Address	Width	Used by
Yes	SPI_CNT0	0x10142000	2
Yes	SPI_DATA0	0x10142002	1
Yes	NSPI_CNT0	0x10142800	4
Yes	NSPI_DONE0	0x10142804	4
Yes	NSPI_BLKLEN0	0x10142808	4
Yes	NSPI_FIFO0	0x1014280C	4
Yes	NSPI_STATUS0	0x10142810	4
Yes	? Same as SPICARD + 0x814. Unused by SPI sysmodule.	0x10142814	4
Yes	? Unused by SPI sysmodule.	0x10142818	4
Yes	? Unused by SPI sysmodule.	0x1014281C	4
Yes	SPI_CNT1	0x10143000	2
Yes	SPI_DATA1	0x10143002	1
Yes	NSPI_CNT1	0x10143800	4
Yes	NSPI_DONE1	0x10143804	4
Yes	NSPI_BLKLEN1	0x10143808	4
Yes	NSPI_FIFO1	0x1014380C	4
Yes	NSPI_STATUS1	0x10143810	4
Yes	? Same as SPICARD + 0x814. Unused by SPI sysmodule.	0x10143814	4
Yes	? Unused by SPI sysmodule.	0x10143818	4
Yes	? Unused by SPI sysmodule.	0x1014381C	4
Yes	SPI_CNT2	0x10160000	2
Yes	SPI_DATA2	0x10160002	1
Yes	NSPI_CNT2	0x10160800	4
Yes	NSPI_DONE2	0x10160804	4
Yes	NSPI_BLKLEN2	0x10160808	4
Yes	NSPI_FIFO2	0x1016080C	4
Yes	NSPI_STATUS2	0x10160810	4
Yes	? Same as SPICARD + 0x814. Unused by SPI sysmodule.	0x10160814	4
Yes	? Unused by SPI sysmodule.	0x10160818	4
Yes	? Unused by SPI sysmodule.	0x1016081C	4

There are two register interfaces: the old NDS/DSi one and an alternative faster interface introduced with the 3DS.

To toggle between those interfaces, use the CFG11_SPI_CNT register.

SPI_CNT

This is the old NDS/DSi SPI interface.

Bits	Name
0-1	Baudrate (0=4MHz, 1=2MHz, 2=1MHz, 3=512KHz)
2-6	This was added with 3DS.
7	Busy Flag (0=Ready, 1=Busy) (presumably Read-only)
8-9	Device Select (0=Powerman., 1=Firmware, 2=Touchscreen)
10	Transfer Size (0=8bit/Normal, 1=16bit/Bugged)
11	Chipselect Hold (0=Deselect after transfer, 1=Keep selected)
12-13	Not used (Zero)
14	Interrupt Request (0=Disable, 1=Enable)
15	SPI Bus Enable (0=Disable, 1=Enable)

NSPI_CNT

This is an alternative faster interface introduced with the 3DS.

Bits	Name
0-2	Baudrate?
6-7	Device Select
12	Bus mode 0=1 bit, 1=4 bit
13	Transfer Direction? (0=Incoming, 1=Outgoing)
15	Busy/enable

Device id	Device select bits
0, 3, >=6	0
1, 4	1
2, 5	2

Device id	Used baudrate
3	5
0	2

NSPI_DONE

This register reads as 1 after starting a transfer. When the transfer is finished, a 0 has to be written to this register. This is probably the Chip Select line.

NSPI_BLKLEN

The number of bytes to be sent/read is written to this register.

NSPI_FIFO

32-bit FIFO for reading/writing the SPI payload.

NSPI_STATUS

Bit0: FIFO busy. At transfer start and every 32 bytes the FIFO becomes busy.