Emmc Cid | Decoder

# Python 3 example: parse 128-bit CID hex string (big-endian bytes)
def parse_cid(cid_hex):
    b = bytes.fromhex(cid_hex)
    if len(b) != 16:
        raise ValueError("CID must be 16 bytes")
    val = int.from_bytes(b, 'big')
    def get(bits_high, bits_low):
        width = bits_high - bits_low + 1
        return (val >> bits_low) & ((1 << width) - 1)
    # offsets (bit positions where 0 is LSB)
    mid = get(127,120)
    oid = get(119,104)
    pnm = get(103,64)
    prv = get(63,56)
    psn = get(55,24)
    mdt = get(23,12)
    crc  = get(11,5)
    end  = get(0,0)
    # decode ascii fields
    oid_str = oid.to_bytes(2,'big').decode('ascii',errors='replace')
    pnm_str = pnm.to_bytes(5,'big').decode('ascii',errors='replace')
    prv_major = (prv >> 4) & 0xF
    prv_minor = prv & 0xF
    # MDT: year offset high 8 bits, month low 4 bits — many eMMC: year = 1997 + year_offset? Check spec.
    year = 2000 + ((mdt >> 4) & 0xFF)
    month = mdt & 0xF
    return 
        "MID": mid, "OID": oid_str, "PNM": pnm_str,
        "PRV": f"prv_major.prv_minor", "PSN": psn,
        "MDT": "year": year, "month": month, "CRC7": crc, "end": end

Many routers, set-top boxes, and Android TV boxes require specific flash tools (MPTools). These tools often ask for the CID or require a "CID replacement" to restore a corrupted bootloader. Decoding helps match the correct firmware template.

Let’s decode a real CID from a SanDisk eMMC used in a Chromebook.

Raw CID: 45010053454d303447d301d4935400b2 emmc cid decoder

Decoded:

What this tells you: This chip is a 4GB eMMC manufactured in February 2011. If your device expects a 32GB eMMC, you now know it has been swapped. Additionally, an old manufacturing date suggests the chip may have worn-out NAND cells, explaining boot failures. # Python 3 example: parse 128-bit CID hex

The easiest method. Several websites offer free eMMC CID decoding.

Popular online decoders:

How to use:

Pros: No installation, instant results.
Cons: Privacy concerns (don’t paste sensitive serial numbers on unknown sites). Many routers, set-top boxes, and Android TV boxes

If the device won't boot, you need an eMMC hardware programmer like:

These tools read the CID directly via the eMMC bus (CLK, CMD, D0) using a soldered or pogo-pin connection.