PXI Registers

Protocol

The communication protocol for normal PXI commands is documented below. The size of cmd_buf is calculated from the cmd_hdr. With newer FIRM the total size for command header + buffer must be at most 0x40 words, otherwise Process9 will panic.

Each pxi_id corresponds to a Process9 PXI command-handler thread which handles the actual command processing. With newer FIRM the pxi_id must be in a certain range.

There's a dedicated Process9 thread for receiving data from PXI, once it finishes receiving a request it copies the cmd_buf into a buffer for the corresponding pxi_id then signals an event so that the cmd-handler thread can process it. Once a cmd-handler thread finishes processing a command, the thread itself then sends the response over PXI. This means that multiple commands for different pxiIDs can be be handled at the same time, even when one cmd-handler completely hangs/etc for example.

Request

A11->A9 (u32) pxi_id
A11->A9 (u32) cmd_hdr
A11->A9 (u32[]) cmd_buf

Response

A9->A11 (u32) pxi_id
A9->A11 (u32) cmd_hdr
A9->A11 (u32[]) cmd_buf

Registers

Old3DS	Name	Address	Width	Used by
Yes	PXI_SYNC9	0x10008000	4
Yes	PXI_????9	0x10008003	1
Yes	PXI_CNT9	0x10008004	4
Yes	PXI_RECV_FIFO9	0x10008008	4
Yes	PXI_SYNC11	0x10163000	4
Yes	PXI_CNT11	0x10163004	4
Yes	PXI_SEND11	0x10163008	4
Yes	PXI_RECV_11	0x1016300C	4

The PXI registers are similar to those on DS.

PXI_SYNC

Bit	RW	Description
0-3	R	Data input from PXI_SYNC Bit8-11 of remote CPU (00h..0Fh)
8-11	R/W	Data output to PXI_SYNC Bit0-3 of remote CPU (00h..0Fh)
13	W	Send IRQ to remote CPU (0=None, 1=Send IRQ)
14	R/W	Enable IRQ from remote CPU (0=Disable, 1=Enable)
23	?	?

PXI_CNT

Bit	RW	Description
0	R	Send Fifo Empty Status (0=Not Empty, 1=Empty)
1	R	Send Fifo Full Status (0=Not Full, 1=Full)
2	R/W	Send Fifo Empty IRQ (0=Disable, 1=Enable)
3	W	Send Fifo Clear (0=Nothing, 1=Flush Send Fifo)
8	R	Receive Fifo Empty (0=Not Empty, 1=Empty)
9	R	Receive Fifo Full (0=Not Full, 1=Full)
10	R/W	Receive Fifo Not Empty IRQ (0=Disable, 1=Enable)
14	R/W	Error, Read Empty/Send Full (0=No Error, 1=Error/Acknowledge)
15	R/W	Enable Send/Receive Fifo (0=Disable, 1=Enable)