Gamecards

A 3DS gamecard

Close-up of PCB

Physical interface

The 3DS gamecards have the same physical interface as regular DS and DSi gamecards. There is only a minor cosmetic difference in the plastic case, which has a small extruding notch on the top-right side. As such, it prevents insertion of the gamecard into old Nintendo DS or DSi systems.

When modifying the case so that the 3DS gamecard fits in a DS or DSi system, those systems will refuse to detect the gamecard and show no banner icon.

Pin	Name	Description
1	GND	Ground
2	CLK	Clock. Frequencies 6.7MHz and 4.2MHz)
3	NC	Not connected. Possibly used to program cards.
4	RCS	ROM select, active low. Pulled low to start a ROM transfer.
5	RST	Reset, active low.
6	ECS	Savegame chip select, active low. Pulled low to start a savegame SPI transfer.
7	IRQ	Removal detection.
8	VCC	Powersupply 3.3V.
9	DAT0	Bidirectional data bus.
10	DAT1	Bidirectional data bus.
11	DAT2	Bidirectional data bus.
12	DAT3	Bidirectional data bus.
13	DAT4	Bidirectional data bus.
14	DAT5	Bidirectional data bus.
15	DAT6	Bidirectional data bus / SPI data from savegame chip.
16	DAT7	Bidirectional data bus / SPI data to savegame chip.
17	GND	Ground

Protocol

The communication protocol between the 3DS system and the 3DS gamecard has changed almost completely in comparison with the DS and DSi gamecard communication protocol.

After the seventh transfer, commands change size from 8 bytes to 16 bytes. Possibly a new encryption is used, such as AES CTR.

Here's a set of sample gamecard commands that a 3DS sends to a 3DS gamecard:

Size	Command	Description
2000	9F00000000000000	Reset
0000	71C93FE9BB0A3B18	Unknown
0004	9000000000000000	Get gamecard ID, response=9000FEC2
0004	9000000000000000	Get gamecard ID, response=9000FEC2
0004	A000000000000000	Unknown
0000	3E00000000000000	Unknown
07EC	82000000000000000000000000000000	Get header
05E3	F32C92D85C9D44DED3E0E41DBE7C90D9	Encrypted, unknown
0332	696B9D8582FB55D31B68CAFE70C74A95	Encrypted, unknown
0332	BAA4812CA0AC9C5D19399530E3ACCCAB	Encrypted, unknown
032E	178E427C22D87ADB86387249A97D321A	Encrypted, unknown
0332	E06019B1BD5C9130ED6A4D9F4A9E7193	Encrypted, unknown
0332	4E0D224862523BBFE2E6255F80E15F37	Encrypted, unknown

The header command has some initial dummy bytes, and eventually responds with a 0x200 byte header. Here's an example for Lego Starwars 3:

0000000: 00 8c 03 00 00 00 04 00 00 00 00 00 00 00 00 00  ................
0000010: b3 cf fb c6 6a b1 cb 20 32 af ce 35 d4 1c 74 c9  ....j.. 2..5..t.
0000020: 8e 6b 27 2f 08 01 28 3b d4 30 de 44 37 f5 b0 46  .k'/..(;.0.D7..F
0000030: 91 59 d7 38 33 48 df 83 fd 71 84 2c 00 00 00 00  .Y.83H...q.,....
0000040: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................
0000050: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................
0000060: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................
0000070: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................
0000080: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................
0000090: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................
00000a0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................
00000b0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................
00000c0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................
00000d0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................
00000e0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................
00000f0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................
0000100: 4e 43 43 48 7a 7f 0e 00 00 8c 03 00 00 00 04 00  NCCHz...........
0000110: 36 34 02 00 00 00 00 00 00 8c 03 00 00 00 04 00  64..............
0000120: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................
0000130: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................
0000140: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................
0000150: 43 54 52 2d 50 2d 41 4c 47 50 00 00 00 00 00 00  CTR-P-ALGP......
0000160: 0c 27 e3 c1 de 7b 2a e2 d3 11 4f 32 a4 ee bf 46  .'...{*...O2...F
0000170: 9a fd 0c f3 52 c1 1d 49 84 c2 a9 f1 d2 14 4c 63  ....R..I......Lc
0000180: 00 04 00 00 00 00 00 00 00 00 00 00 01 03 00 00  ................
0000190: 05 00 00 00 01 00 00 00 00 00 00 00 00 00 00 00  ................
00001a0: 06 00 00 00 1c 0a 00 00 01 00 00 00 00 00 00 00  ................
00001b0: 22 0a 00 00 58 75 0e 00 01 00 00 00 00 00 00 00  "...Xu..........
00001c0: 13 0c 04 26 15 f6 47 c4 c6 32 25 ea 9e 67 f8 a2  ...&..G..2%..g..
00001d0: 7b 15 24 6b 88 fb c7 a9 27 25 7b 84 97 7b 78 7b  {.$k....'%{..{x{
00001e0: a6 5b ee 10 60 bb 6a 68 21 bb ce c6 00 03 5b 7e  .[..`.jh!.....[~
00001f0: 64 fb 6e ac a7 f0 96 0c fb 1f 5a 37 08 77 28 f7  d.n.......Z7.w(.