This page documents the format of NCSD. CTR cart images (CCI) is NCSD, but the same NCSD is for SD card titles and other things as well. CSU is NCSD used for system updates, development tools.
This is a container format which holds CXI files inside.
Overview
NCSD images start with a NCSD header, followed by up to a maximum of 13 NCCH blocks according to spec. The first block(CXI 0) always starts at 0x4000. In most carts the first block contains game code/data. The second block(CXI 1) contains the game "Manual"(title ID for the .CXI containing the Manual always starts with '0005'). In the third block(CXI 2) contains the download play "Child"(The title ID for the .CXI containing the Child always starts with '0006'). The eight block(CXI 7) contains update data(The title ID for the .CXI containing the update data always starts with '8000') The exact contents of NCCH blocks can be determined by looking at the flags.
NCSD header
| Offset | Size | Description |
|---|---|---|
| 0x000 | 0x100 | RSA-2048 SHA-256 signature of the NCSD header |
| 0x100 | 4 | Magic Number 'NCSD' |
| 0x104 | 4 | Size of the NCSD image, in media units (1 media unit = 0x200 bytes) |
| 0x108 | 8 | Title/Program ID |
| 0x110 | 16 | Unknown |
| 0x120 | 0x68=(4+4)*13 | Offset & Length CXI table |
| 0x188 | 8 | CXI Flags: byte[5]-byte[7] indicate content type ( system update, application, manual, ... ) size of media units ( 512*2^byte[6] ) and encryption. |
| 0x190 | 0x68=8*13 | CXI's Title ID table |
| 0x1F8 | 8 | Unknown |
| 0x200 | 4 | Always 0xFFFFFFFF |
| 0x204 | 252 | Padding? |
| 0x300 | 4 | Used ROM size in bytes |
| 0x304 | 28 | Padding |
| 0x320 | 8 | NVer Title ID (Not Present in .CSU) |
| 0x328 | 8 | NVer Title Version (Not Present in .CSU) |
Parts of the first NCCH block's header are found around 0x1000 for whatever reason. NCSD can hold up to 13 CXI (i.e. Mario Kart 7 holds 4 CXIs, most we've seen so far)
The region-specific NVer title for this NCSD presumably must exist on NAND. The NVer title version may also be used to check whether a system update is required before running the app.