Registers #

Old3DS	Name	Address	Width	RW
Yes	NSPI_CNT	0x1000D800	4	RW
Yes	NSPI_DONE	0x1000D804	4	RW
Yes	NSPI_BLKLEN	0x1000D808	4	RW
Yes	NSPI_FIFO	0x1000D80C	4	RW
Yes	NSPI_STATUS	0x1000D810	4	R
Yes	NSPI_AUTOPOLL	0x1000D814	4	RW
Yes	NSPI_INT_MASK	0x1000D818	4	W?
Yes	NSPI_INT_STAT	0x1000D81C	4	RW

NSPI_CNT #

BIT	DESCRIPTION
0-2	Baud Rate
6-7	Unused device select.
12	Bus Mode
13	Transfer Mode (0 = read, 1 = write)
15	Trigger (0 = idle, 1 = busy)

This register seems to have a bug where the lower 8 bits are shifted up by 16 when reading this register.

NSPI_DONE #

Contains 1 when the SPI slave is selected. A 0 is written here on transfer end to deselect the slave.

NSPI_BLKLEN #

BIT	DESCRIPTION
0-20	Transfer size
21-31	Unused

NSPI_FIFO #

BIT	DESCRIPTION
0-31	Data

This FIFO is one way (half-duplex).

NSPI_STATUS #

BIT	DESCRIPTION
0	FIFO Full (0 = not full, 1 = full)

NSPI_AUTOPOLL #

BIT	DESCRIPTION
0-7	Command
16-19	Timeout (Tries = 31<<Baudrate (from NSPI_CNT) + Timeout)
24-26	Bit offset (0-7)
30	Poll for a set or unset bit
31	1 = Enable/Busy

This automatically sends a command to the device and compares the specified bit in the response with bit 30 until it matches or a timeout occurs. Nintendo uses a timeout of 10 which roughly equals 1 second. This is used in Process9 to poll the gamecard SPI flash status register for write operation finished or write enable.

NSPI_INT_MASK #

BIT	DESCRIPTION
0	Transfer finished (1 = disabled)
1	Autopoll success (1 = disabled)
2	Autopoll timeout (1 = disabled)

NSPI_INT_STAT #

BIT	DESCRIPTION
0	Transfer finished (also fires on each autopoll try?)
1	Autopoll success
2	Autopoll timeout

Interrupt ID 23 is fired when any of the bits change to 1 except for interrupts masked in NSPI_INT_MASK. Writing 1 to a bit in this register aknowledges the interrupt.

SPICARD Registers