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The column " Yuan Takes You to Learn: Detailed Explanation of the eMMC Protocol "

abstract

Full text 8100 words, main content

The command of eMMC is introduced in detail, mainly including the following contents:

(1) What are the emmc commands?

(2) Points to note when using different commands

(3) command class classification

(4) command command parameter and response format

1 Introduction

There are many eMMC commands, which can be divided into many categories. The more important ones are class 0/2/4/11.

2.command type

command type	illustrate
bc	Broadcast command without response
bcr	Broadcast command with response
ac	Point-to-point no data transmission
adtc	point-to-point data transmission

Table command type

3. command format

As shown in the figure above, eMMC Command is composed of 48 Bits, and the analysis of each Bits is as follows:

Table command format

Total length 48bits;
It is fixed to start with the start bit value 0 and end with the End Bit value 1;
The transmitter bit indicates the direction of data transmission, 1 means from host to device, that is, write operation, and 0 means device to host, that is, read operation;
Command index indicates the index of the command with 6 bits, and the value range is 0~63;
argument: Some commands need to send parameters, whether to send parameters depends on the specific command;
CRC7 is the CRC check value including Start Bit, Transmission Bit, Command Index and Argument. Through CRC7 protection, the device side will also calculate a CRC value when receiving the CMD. If it is inconsistent with the CRC sent by the host, it will be considered a transmission error;

Note 1: eMMC may not support all commands from 0 to 63, and some commands may not be supported

Note 2: In simple terms, the CRC check means that the sender "divides" (modulo 2) the data to be transmitted by an agreed number, and attaches the remainder to the data and sends it out. After receiving the data, the receiver performs the same "division", and then checks whether the remainder is the same as the received remainder.

If not, it means that the data has changed during transmission. Further reading the introduction in the CRC wiki .

The Command line is a line, so you can see that the 48 bits are transmitted sequentially on the waveform. When looking at the waveform, you need to find the Start bit (from high to low), and then count the offset of the corresponding bit number. Generally, the offset is 2 A bit, see what the corresponding Command is, to analyze the behavior of this segment of the waveform.

4. command class classification

eMMC divides the command index (0~56) into 12 classes, and each class represents a class of functions, including a subset of all commands. Which class commands a specific device supports can be queried through the CCC[95:84] feilds of the CSD register. If bit84 is 1, it means class0 is supported.

In fact, general commands (except discarded classes) will be supported by devices, and it is not complicated. What to pay attention to is the class 11 Command Queue command, some platforms do not support Command Queue, so CMDQ Read and CMDQ Write cannot be done, intelligently use ordinary Read (CMD16 or CMD17) and ordinary Write (CMD24 or CMD25) commands, extremely fast performance It will also be worse.

For Pack Read and Pack Write, although the protocol has this, it is rarely encountered in practice. This function is not flexible enough, and it is considered a tasteless function, but the device generally supports this feature, but the host hardly uses it. So don't spend too much resources on Pack Read/Write.

device command class	class description	note
class 0	basic	basic command
class 1	obsolete	abandoned
class 2	block read	Block data read-related commands, including setting block length, reading single block, and reading multiple blocks
class 3	obsolete	abandoned
class 4	block write	Block data write-related commands, including setting the number of blocks, writing a single block, writing multiple blocks, modifying the device id register, modifying the CSD, and setting the RTC
class 5	erase	Set erase group start address, set erase group end address, erase operation
class 6	write protection	Set write protection, clear write protection, get write protection status of device, get write protection type
class 7	lock device	lock/unlock device
class 8	application-specific	Indicates that the next command is an application-specific command rather than a standard command
class 9	I/O mode	Write registers, set the system into interrupt mode
class 10	security protocols	Continuously transfer data blocks from device to host or from host to device
class 11	command queuing	Execute tasks in the queue
class 12	reserved	\

Table command classification

The above is reproduced from

https://www.cnblogs.com/smartjourneys/p/6657397.html

5. Command command and Response format

Basic commands (class 0 and class 1)

CMD0

Abbr.	Type	Argument	Resp	Description
GO_IDLE_STATE	bc	[31:0] 00000000	None	Resets the Device to idle state
GO_PRE_IDLE_STATE	bc	[31:0] F0F0F0F0	None	Resets the Device to pre-idle state
BOOT_INITIATION	-	[31:0]FFFFFFFA	None	Initiate alternative boot operation

CMD1

Abbr.	Type	Argument	Resp	Description
SEND_OP_COND	bcr	[31:0] OCR without busy	R3	Asks Device, in idle state, to send its Operating Conditions Register contents in the response on the CMD line.

CMD2

Abbr.	Type	Argument	Resp	Description
ALL_SEND_CID	bcr	[31:0] stuff bits	R2	Asks Device to send its CID number on the CMD line

CMD3

Abbr.	Type	Argument	Resp	Description
SET_RELATIVE_ADDR	ac	[31:16] RCA, [15:0] stuff bits	R1	Assigns relative address to the Device

CMD4

Abbr.	Type	Argument	Resp	Description
SET_DSR	bc	[31:16] DSR, [15:0] stuff bits	-	Programs the DSR of the Device

CMD5

Abbr.	Type	Argument	Resp	Description
SLEEP_AWAKE	ac	[31:16] RCA, [15]Sleep/Awake, [14:0] stuff bits	R1b	Toggles the Device between Sleep state and Standby state.

CMD6

Abbr.	Type	Argument	Resp	Description
SWITCH	ac	[31:26] Set to 0, [25:24] Access, [23:16] Index, [15:8] Value, [7:3] Set to 0, [2:0] Cmd Set	R1b	Switches the mode of operation of the selected Device or modifies the EXT_CSD registers.

CMD7

Abbr.	Type	Argument	Resp	Description
SELECT/DESELECT_CARD	ac	[31:16] RCA, [15:0] stuff bits	R1/R1b	Command toggles a device between the standby and transfer states or between the programming and disconnect states.

CMD8

Abbr.	Type	Argument	Resp	Description
SEND_EXT_CSD	adtc	[31:0] stuff bits	R1	Device sends its EXT_CSD register as a block of data.

CMD9

Abbr.	Type	Argument	Resp	Description
SEND_CSD	ac	[31:16] RCA, [15:0] stuff bits	R2	Addressed Device sends its Device-pecific data (CSD) on the CMD line.

CMD10

Abbr.	Type	Argument	Resp	Description
SEND_CID	ac	[31:16] RCA, [15:0] stuff bits	R2	Addressed Device sends its Device identification (CID) on CMD the line.

CMD12

Abbr.	Type	Argument	Resp	Description
STOP_TRANSMISSION	ac	[31:16] RCA, [15:1] stuff bits, [0] HPI	R1/R1b	Forces the Device to stop transmission. If HPI flag is set the device shall interrupt its internal operations in a well-defined timing.

CMD13

Abbr.	Type	Argument	Resp	Description
SEND_STATUS	ac	[31:16] RCA, [15] SQS, [14:1] stuff bits, [0] HPI	R1	In case SQS bit = 0: Addressed Device sends its status register. If HPI flag is set the device shall interrupt its internal operations in a well-defined timing. In case SQS bit = 1: indicate that this is a QSR query. In response device shall send the QSR (Queue Status Register). In this case HPI must be set to ‘0’

CMD14

Abbr.	Type	Argument	Resp	Description
BUSTEST_R	adtc	[31:0] stuff bits	R1	A host reads the reversed bus testing data pattern from a Device.

CMD15

Abbr.	Type	Argument	Resp	Description
GO_INACTIVE_STATE	ac	[31:16] RCA, [15:0] stuff bits	-	Sets the Device to inactive state

CMD19

Abbr.	Type	Argument	Resp	Description
BUSTEST_W	adtc	[31:0] stuff bits	R1	A host sends the bus test data pattern to a Device

NOTE 1 - CMD7, R1 while selecting from Stand-By State to Transfer State; R1b while selecting from Disconnected State to Programming State.
NOTE 2 - CMD12, RCA in CMD12 is used only if HPI bit is set. The argument does not imply any RCA check on the device side.
NOTE 3 - CMD12, R1 for read cases and R1b for write cases.

Block-oriented read commands (class 2)

CMD16

Abbr.	Type	Argument	Resp	Description
SET_BLOCKLEN	ac	[31:0] block length	R1	Sets the block length (in bytes) for all following block commands (read and write). Default block length is specified in the CSD

CMD17

Abbr.	Type	Argument	Resp	Description
READ_SINGLE_BLOCK	adtc	[31:0] data address	R1	Reads a block of the size selected by the SET_BLOCKLEN command

CMD18

Abbr.	Type	Argument	Resp	Description
READ_MULTIPLE_BLOCK	adtc	[31:0] data address	R1	Continuously transfers data blocks from Device to host until interrupted by a stop command, or the requested number of data blocks is transmitted If sent as part of a packed read command, the argument shall contain the first read data address in the pack (address of first individual read command inside the pack).

CMD21

Abbr.	Type	Argument	Resp	Description
SEND_TUNING_BLOCK	adtc	[31:0] stuff bits	R1	128 clocks of tuning pattern (64 byte in 4bit mode or 128 byte in 8 bit mode) is sent for HS200 optimal sampling point detection.

NOTE 1 - CMD17 & CMD18, Data address for media =<2 32="" gb="" is="" a="" bit="" byte="" address="" and="" data="" for="" media=""> 2GB is a 32 bit sector (512 B) address.
NOTE 2 - CMD17, The transferred data must not cross a physical block boundary, unless READ_BLK_MISALIGN is set in the CSD register.

Block-oriented write commands (class 4)

CMD23 (default)

Abbr.	Type	Argument	Resp	Description
SET_BLOCK_COUNT	ac	[31] Reliable Write Request, [30] ‘0’ non- packed, [29] tag request,[28:25] context ID, [24]: forced programming, [23:16] set to 0, [15:0] number of blocks	R1	Defines the number of blocks (read/write) and the reliable writer parameter (write) for a block read or write command.

CMD23 (packed)

Abbr.	Type	Argument	Resp	Description
SET_BLOCK_COUNT	ac	[31] set to 0, [30] ‘1’ packed, [29:16] set to 0, [15:0] number of blocks	R1	Defines the number of blocks (read/write) for the following packed write command or for the header of the following packed read command.

CMD24

Abbr.	Type	Argument	Resp	Description
WRITE_BLOCK	adtc	[31:0] data address	R1	Writes a block of the size selected by the

SET_BLOCKLEN command. |

CMD25

Abbr.	Type	Argument	Resp	Description
WRITE_MULTIPLE_BLOCK	adtc	[31:0] data address	R1	Continuously writes blocks of data until a STOP_TRANSMISSION follows or the requested number of block received. If sent as a packed command (either packed write, or the header of packed read) the argument shall contain

the first read/write data address in the pack (address of first individual command inside the pack). |

CMD26

Abbr.	Type	Argument	Resp	Description
PROGRAM_CID	adtc	[31:0] stuff bits	R1	Programming of the Device identification register. This command shall be issued only once. The Device contains hardware to prevent this operation after the first programming. Normally this command is reserved for the manufacturer.

CMD27

Abbr.	Type	Argument	Resp	Description
PROGRAM_CSD	adtc	[31:0] stuff bits	R1	Programming of the programmable bits of the CSD.

CMD49

Abbr.	Type	Argument	Resp	Description
SET_TIME	adtc	[31:0] stuff bits	R1	Sets the real time clock according to the RTC information in the 512 B data block.

NOTE 1 - CMD24 & CMD25, Data address for media =<2 32="" gb="" is="" a="" bit="" byte="" address="" and="" data="" for="" media=""> 2GB is a 32 bit sector (512 B) address.
NOTE 2 - CMD24, The transferred data must not cross a physical block boundary, unless READ_BLK_MISALIGN is set in the CSD register.

Block-oriented write protection commands (class 6)

Erase commands (class 5)

I/O mode commands (class 9)

Lock Device commands (class 7)

Application-specific commands (class 8)

Security Protocols (class 10)

Command Queue (Class 11)

本部分你转载自

eMMC Commands_子曰小玖的博客-CSDN博客

参考

[1] https://www.cnblogs.com/smartjourneys/p/6657397.html

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This article is organized based on public information and aims to introduce more storage knowledge. The articles contained in the article are only the author's opinion and do not constitute investment or commercial advice. This article is only for learning and communication, not for commercial use. If you have any questions or infringements, please contact the author.

[Yuan takes you to learn: detailed explanation of eMMC protocol 20] Detailed explanation of emmc command (cmd) and response (resp)