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eMMC (Embedded MultiMediaCard)

eMMC (Embedded MultiMediaCard) is a type of non-volatile memory storage commonly used in mobile devices, such as smartphones, tablets, and embedded systems. It integrates both flash memory and a flash memory controller into a single package, making it a compact and cost-effective solution for storage needs.

Key Features

eMMC is designed for soldered-down, space-constrained applications. It uses the same interface and protocol as SD cards, making integration easier. eMMC offers higher performance and better durability than SD cards. It supports features like wear leveling and bad block management.

Relationship with SD Cards

eMMC and SD cards share a similar interface and protocol, known as the SPI (Serial Peripheral Interface) bus. However, there are notable differences between the two:

  • Physical Form Factor: eMMC is soldered onto the device's circuit board, while SD cards are removable.
  • Performance: eMMC generally provides faster read and write speeds compared to most SD cards.
  • Durability: eMMC tends to be more durable than SD cards due to its integration and soldered connection.
  • Endurance: eMMC typically has higher endurance (read/write cycles) compared to consumer-grade SD cards.

eMMC vs. NAND/NOR Flash Memory

NAND and NOR are two primary types of flash memory used in various devices, including SSDs, USB drives, and embedded systems.

NAND Flash Memory:

  • Used in SSDs, USB drives, memory cards, etc.
  • Higher storage density, lower cost per gigabyte.
  • Faster write speeds compared to NOR.
  • Commonly used for mass storage.

NOR Flash Memory:

  • Used in BIOS chips, firmware storage, bootable devices, etc.
  • Slower write speeds compared to NAND.
  • Typically lower storage density than NAND.
  • Suitable for applications requiring random access and execution.

In contrast, eMMC is an embedded storage solution that combines flash memory and a controller. It's optimized for space-constrained applications and offers good performance and durability without requiring external controllers. While NAND and NOR are more versatile and can be used in a wider range of applications, eMMC is specifically tailored for embedded systems and mobile devices where space, performance, and integration are critical.

Identifying eMMC

Identifying eMMC (Embedded MultiMediaCard) pins using a logic analyzer involves capturing and analyzing the signals on the pins to identify patterns that correspond to the eMMC communication protocol. eMMC uses a standard communication protocol like SDIO, SPI or a modified version of it, so you'll need to look for specific signal patterns that indicate data transfer and communication operations. Here's a step-by-step guide on how to identify eMMC pins using a logic analyzer:

  1. Gather Equipment:
    • Obtain a logic analyzer that is capable of capturing signals at the frequencies used by the eMMC protocol. The logic analyzer should have enough channels to monitor all the relevant pins.
  2. Identify Power and Ground Pins:
    • Refer to the eMMC datasheet or device documentation to identify the power and ground pins. Typically, these pins are labeled and grouped together.
  3. Identify Clock Signal (CLK):
    • The eMMC protocol uses a clock signal to synchronize data transfers. Look for a pin that exhibits regular high-frequency oscillations. This is likely the CLK (clock) pin.
  4. Identify Data Lines (DAT0 - DAT7):
    • eMMC data lines (DAT0 to DAT7) are used to transmit and receive data. You can identify these lines by their proximity to the CLK pin and their signal behavior during data transfer.
    • Data lines might show transitions in response to clock changes, indicating data being shifted in or out.
  5. Capture Signals:
    • Connect the logic analyzer probes to the CLK and DAT0-DAT7 pins of the eMMC.
    • Configure the logic analyzer to capture signals at a suitable sample rate. Set trigger conditions to start capturing when a specific signal pattern is detected.
  6. Start Capturing:
    • Begin capturing signals while performing actions that involve eMMC communication, such as reading or writing data.
  7. Analyze Captured Data:
    • Analyze the captured signals to identify patterns that match the eMMC communication protocol.
    • Look for synchronous data transfers that correspond to the clock signal (CLK) and data lines (DAT0-DAT7).
  8. Decoding:
    • If your logic analyzer supports protocol decoding, apply the appropriate eMMC protocol decoder to the captured signals. This can help you visualize data packets, command sequences, and responses.
  9. Compare with Datasheet:
    • Refer to the eMMC datasheet or technical documentation to confirm that the signal patterns you've identified match the expected behavior.
  10. Trial and Error:
    • If you're unsure about the signals' meaning, you might need to experiment with different actions and observe how the signals change.

BlackHat "Hacking hardware with a $10 SD Card Reader"

We did a presentation on identifying the pins needed to communicate with eMMC as well as using a cheap SDCard reader/writer for dumping. Check out the whitepaper and video below

BlackHat Whitepaper & Video