Emmc Cid Decoder

On any Linux-based system (including Android), the eMMC CID is exposed via sysfs if the kernel supports it.

cat /sys/block/mmcblk0/device/cid

Alternatively, using mmc-utils:

mmc extcsd read /dev/mmcblk0 | grep CID

On Android (rooted):

su
cat /sys/block/mmcblk0/device/cid

The CID ends with a 7-bit CRC (bits [7:1]) that protects the CID’s integrity. A full-featured decoder should verify this CRC. The polynomial for eMMC CID CRC7 is:

[ CRC7 = x^7 + x^3 + 1 \quad (0x09) ]

Initial value: 0x00.

If your decoder does not validate the CRC, you risk acting on corrupted data. Professional tools (like mmc-utils) include this check.

Given a raw 32-character hex string (e.g., 1501004D34474255015A1AC0E80100), the decoder performs:

Once you have the 32-character hex string, you need a decoder. Here are the most common options, from beginner-friendly to advanced. emmc cid decoder

The 128 bits are divided into 16 bytes (BE). The JESD84-B51 standard defines the following fields:

| Byte (offset) | Field | Name | Size (bits) | Description | | :--- | :--- | :--- | :--- | :--- | | 15 | MID | Manufacturer ID | 8 | Unique JEDEC-assigned ID | | 14 | CBX | Card/BGA | 2 | Package type (BGA / removable) | | 13-12 | OID | OEM/Application ID | 16 | OEM identifier (optional) | | 11-8 | PNM | Product Name | 32 | ASCII string (6 chars, left-justified, space-padded) | | 7 | PRV | Product Revision | 8 | Major/Minor BCD (e.g., 0x12 = v1.2) | | 6-4 | PSN | Product Serial Number | 24 | Unique device serial number | | 3-2 | MDT | Manufacturing Date | 12 | Year (BCD) + Month (BCD) | | 1-0 | CRC | CID CRC | 7+1 | Checksum (7 bits) + 1 reserved bit |

Note: byte offset counts from most significant byte (byte 15) to least (byte 0). Many decoders use 0‑based array indexing starting at CID[0] = MSB.

Tools like MMC Utility (by Rusolut) or Flash Extractor include advanced decoders that also validate CRC and parse extended CSD registers linked to the CID. On any Linux-based system (including Android), the eMMC

Raw CID: 1501004242473541021A79C0D5012B

When decoded:

As you can see, manual decoding is tedious and error-prone. Hence, the need for a reliable eMMC CID decoder.

Once you have the 32-character hexadecimal string, you need to decode it. You have several options: On Android (rooted): su cat /sys/block/mmcblk0/device/cid