print(f"Raw CID: cid_hex") print(f"Manufacturer ID (MID): 0xresult['MID']:02X") print(f"Device Type (CBX): 0xresult['CBX']:02X") print(f"OEM/App ID (OID): 0xresult['OID']:02X") print(f"Product Name (PNM): pnm_bytes") print(f"Product Revision (PRV): prv_major.prv_minor") print(f"Serial Number (PSN): 0xresult['PSN']:08X") print(f"Manufacturing Date (MDT): Month: month, Year: year") print(f"CRC7: 0xresult['CRC7']:02X")
Before diving into decoders, it‘s essential to understand what the CID register actually contains. The CID is a mandatory 128-bit register defined by the JEDEC standard (JESD84-B51) and plays a critical role during the device identification phase of the eMMC protocol.
An 8-bit identifier typically used by the manufacturer to identify the customer or a specific product line.
| Operating System | Method / Command | Description | Example / Notes | | :--- | :--- | :--- | :--- | | | cat /sys/block/mmcblk0/device/cid | Directly reads the raw hex value from the sysfs interface. | Replace mmcblk0 with the correct block device. | | Linux | sudo mmc cid read /dev/mmcblk0 | Part of mmc-utils package; prints the CID data from the device. | | Android | adb shell cat /sys/block/mmcblk0/device/cid | Uses ADB to read the CID from the Android device's sysfs. | The eMMC block device might be mmcblk0 or mmcblk1 . | | Android | EmmcGetHuid() | A HarmonyOS API function call to retrieve the CID. | Part of the HarmonyOS device development platform. | | Windows | Manufacturer Tools | Relies on specific vendor tools (e.g., from Samsung or SiliconGo). | May require physical ISP connection. | | OpenWrt | cat /tmp/sysinfo/emmc_cid | Some builds will output the CID to a system information file. | Not always available by default. |
# Display all device information including decoded CID mmc extcsd read /dev/mmcblk0 emmc cid decoder
For developers interested in creating custom CID decoding solutions, here‘s a simple Python implementation to get started:
Indicates the hardware and firmware revision of the controller.
| Field | Bytes | Description | | :--- | :--- | :--- | | | 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. |
When you run a raw string through a MultiCID Decoder , it parses the bits into these specific fields: sdmmc eMMC Decode CID properly - NXP Community | Operating System | Method / Command |
An is a software tool or script that translates this raw, hexadecimal 128-bit string into human-readable data. This article explores the structure of the CID register, how decoding works, and why it is critical for hardware engineering and digital forensics. What is an eMMC CID?
The original standard used 1997 as the base year offset. For eMMC 4.41 and later devices, the interpretation may change depending on the EXT_CSD_REV value. Some implementations shift the base year to 2013 for newer devices.
The eMMC CID decoder is an essential utility that bridges the gap between raw hardware identification and practical usability. By translating a 128-bit hexadecimal code into actionable data, it provides critical insights into an embedded device's origin and identity. Whether you are an engineer verifying a production line, a technician recovering a bricked system, or a developer implementing hardware-level security, mastering the extraction and interpretation of the eMMC CID is a fundamental and rewarding skill in the world of embedded storage.
: While the CID register is theoretically programmable on some devices, in practice it's typically locked after manufacturing. USB-based card readers cannot access or modify CID information—a native MMC/SD host controller is required. | | Android | adb shell cat /sys/block/mmcblk0/device/cid
# Bytes 10-13: Product Serial Number (PSN) psn = int.from_bytes(raw_bytes[10:14], byteorder='big')
An eMMC CID decoder is a software tool or algorithm used to decode and extract the information stored in the CID number. The decoder takes the CID number as input and outputs the individual fields, providing a clear understanding of the eMMC chip's characteristics.
# Convert hex string to bytes cid_bytes = bytes.fromhex(cid_hex)