The Ultimate Guide to Understanding and Using an eMMC CID Decoder
eMMC (Embedded MultiMediaCard) is the standard storage used in smartphones, tablets, and many automotive infotainment systems. Every eMMC chip has a Card Identification (CID) Register. emmc cid decoder
In the world of embedded storage, the eMMC (embedded MultiMediaCard) is the silent workhorse powering billions of devices—from smartphones and tablets to Raspberry Pi boards, automotive infotainment systems, and industrial IoT modules. While users rarely interact with their storage directly, every eMMC chip carries a unique, immutable fingerprint known as the CID (Card Identification Register) . The Ultimate Guide to Understanding and Using an
| Field | Bytes | Description |
| :--- | :--- | :--- |
| MID | 0 | Manufacturer ID. I mapped the most common IDs (Samsung, SanDisk, Toshiba, Micron) in the script. |
| OID | 1-2 | OEM/Application ID. Usually 2 characters hex identifying the card customer or specific application. |
| PNM | 3-8 | Product Name. ASCII string (up to 6 characters). Often model numbers like "BJTD4R" or "8GTF4". |
| PRV | 9 | Product Revision. Binary Coded Decimal (BCD). 0x18 = Rev 1.8. |
| PSN | 10-13 | Product Serial Number. A 32-bit unique integer. |
| MDT | 14 | Manufacturing Date. 4 bits for Month (1-12), 4 bits for Year (Offset from 1997). |
| CRC | 15 | Cyclic Redundancy Check. The script verifies this to ensure the CID is valid and not corrupted. | Method 1: From a Linux/Android System (Root Required)
CRC7 Checksum: A 7-bit checksum used to verify that the CID data has not been corrupted during transmission. Why Decoding Matters
sudo mmc extcsd read /dev/mmcblk0 | grep CID
On any Linux-based system (including Android), the eMMC CID is exposed via sysfs if the kernel supports it.