eMMC Summary

1. overview

• 11-wire bus : clock, data strobe, 1 bit command , 8 bit data bus
• DAT0 low :busy

2. Message Tokens

• Command: token that starts an operation

• Host to device

• CMD line

• Response: answer to previously received command

• Device to host

• CMD line

• Data

• Host to device or versa

• Data line:1,4 or 8

 

3. Command

1. command format
2. common command

• CMD0(with arg 0x0000 0000(GO_IDLE_STATE)

• CMD1(SEND_OP_COND)

Response:R3

Ask device(in idle state) to send OCR register contents in response on CMD line

Repeat until busy bit in response is cleared

• CMD2(ALL_SEND_CID)

• Asking all devices for its unique device identification(CID) number

• If CID bits not match, the device stop sending, remain in ready state and wait

• Only one device send CID number to host successfully

• If successful, device into identification state

• CMD3(SET_RELATIVE_ADDR)

• Assign device a relative device address(RCA)

• CMD15(GO_INACTIVE_STATE)

• Send an addressed device into inactive state

• CMD40(GO_IRQ_STATE)

​​​​​​​• Set the device into interrupt mode

• CMD7(SELECT/DESELECT_CARD)​​​​​​​

•Between stand-by state and transfer state

•Between disconnect state and programming state

•RCA value 0x0000 is reserved to set all devices into stand-by state

• CMD13(SEND_STATUS)
• CMD12:stop transmission
• Block read

•Single block: CMD17

•Multiple block : CMD18

• Block write

•Single block: CMD24

•Multiple block: CMD25

• SET_BLOCK_COUNT(CMD23):in multiply read/write
• CMD16 : set block length for following read/write
• Erase

•CMD35:set start address

•CMD36:set end address

•CMD38 0x00000000 :start erase process

• CMD42: lock/unlock device
• CMD5: sleep/awake
• CMD6: switch the mode of operation or modify the EXT_CSD register

4. Response

• R1/R1b

​​​​​​​

• R2(CID,CSD register):CMD2,9,10

• R3(OCR register):CMD1

​​​​​​​

• R4(Fast I/O):CMD39
• ​​​​​​​R5(interrupt request):CMD40

​​​​​​​

5. Memory Array Partitioning

•read/write: Block—multiple bytes

•Erase: Erase Group—multiple blocks

•Write protected : WP-Group—multiple Erase Group

6. Mode

• access mode

  • Byte access mode : up to 2GB of density

  • Sector access mode : higher than 2GB of density

• ​​​​​​​operation mode

7. Partition Management