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eMMC

Table of Contents

Commands

Document eMMC Commands.

Command Table

Command Data Line Response Description Version Addend
CMD1 - R3 Ask device to send its OCR.
CMD6 b R1b Switches the mode of operation of the selected Device or modifies the EXT_CSD registers
CMD9 - R2 Obtain CSD on the CMD line.
CMD7 - R1/R1b Command toggles a device between the standby and transfer or between the programming and disconnect.
CMD13 - R1 Addressed card sends its status register.
CMD8 R R1 Device sends its EXT_CSD register as a block of data
CMD18 R R1 Read multiple blocks.
CMD17 R R1 Read single bolck.
CMD24 R R1 Write single block.
CMD25 R R1 Write multiple blocks.

CMD6

  • Unlike SD, eMMC cards don't have a configuration register to notify supported bus width.
  • The speed mode supported by the card can be determined by the DEVICE_TYPE (196th byte) of EXT_CSD.

Multiple Block Xfer Command

The following commands will continuously write/read blocks of data until a STOP_TRANSMISSION (CMD12) follows or the requested number of block (Specified by CMD23) received.

  • CMD18 - Read multiple blocks.
  • CMD25 - Write multiple blocks.
Creation Date: 2023/08/17, Last modified: 2023/10/27, Author: Siyuan Liu

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