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.
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 always starts at 0x4000. In most carts the first block contains game code/data, the second block contains the download play "child" and the third block contains potential system updates. Additionally, an extra partition may contain an title for installation on SD card. 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 | Loader Title ID |
| 0x328 | 8 | Loader Title Version |
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)