SD物理层简化规范2.00版解读

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"SD Specifications Part1 Physical Layer Simplified Specification Version 2.00" 这篇文档是SD卡协会发布的SD物理层简化的规范，版本2.00，由松下、闪迪和东芝公司共同参与的技术委员会制定。该文档详细阐述了关于SD卡的多个关键知识点，包括命令操作、响应机制、传输模式以及寄存器和ECC（错误校验码）的相关内容。 1. SD命令详细描述： SD卡支持一系列命令来执行不同的功能，如读取、写入、设置卡的状态等。这些命令包括但不限于：CMD0（初始化）、CMD1（发送操作条件）、CMD2（发送CID，卡标识号）、CMD3（读取 RCA，相对卡地址）、CMD6（切换电压/设置模式）、CMD8（发送电压确认）、CMD9（读CSD，卡特定数据）、CMD12（停止传输）、CMD16（设置块长度）、CMD17（读单块）、CMD18（连续读块）、CMD24（写单块）、CMD25（连续写块）等。每种命令都有其特定的用途和响应机制。 2. SD响应详细描述：对于每个发送给SD卡的命令，卡都会返回一个响应，表明命令是否成功执行。响应通常包括R1、R1b、R2、R3、R5、R6、R7等类型，每种响应格式不同，携带的信息也各异，例如错误状态、卡状态、CRC校验等。 3. SD传输模式详细描述： SD卡支持多种传输模式，包括单比特传输（SPI模式）和多比特传输（1位SD模式、4位SD模式和8位SDHC/SDXC模式）。在多比特模式下，数据可以并行传输，显著提高数据传输速率。这些模式的选择和切换通常通过CMD6命令完成，并且需要考虑卡和主机之间的兼容性。 4. SD寄存器及ECC介绍： SD卡内部包含多个寄存器，用于存储和控制卡的操作状态。比如，CSD（卡特定数据）寄存器包含了卡的容量、速度等级等信息；CID（卡标识）寄存器则存储了制造商信息和卡的唯一ID。ECC（Error Correction Code）是SD卡中的一个重要特性，用于检测和纠正数据传输过程中可能出现的错误，确保数据的完整性。ECC通常通过CRC校验和错误校正算法实现，如BCH或 Reed-Solomon编码。这个规范的发布日期为2006年9月25日，相比于之前的1.10版本，2.00版本可能引入了新的特性和改进，以适应不断发展的存储需求和技术进步。SD卡协会是出版和维护此规范的组织，负责制定和更新SD卡的标准，以促进其在全球范围内的兼容性和互操作性。

Physical Layer Simplified Specification Version 2.00

3. SD Memory Card System Concept

Description here is a blank for the Simplified Specification.

3.1 Read-Write Property

In terms of read-write property, two types of SD Memory Cards are defined:

• Read/Write (RW) cards (Flash, One Time Programmable - OTP, Multiple Time Programmable -

MTP). These cards are typically sold as blank (empty) media and are used for mass data storage,

end user video, audio or digital image recording

• Read Only Memory (ROM) cards. These cards are manufactured with fixed data content. They are

typically used as a distribution media for software, audio, video etc.

3.2 Supply Voltage

In terms of operating supply voltage, two types of SD Memory Cards are defined:

• High Voltage SD Memory Cards that can operate within the voltage range of 2.7-3.6 V.

• Dual Voltage SD Memory Cards –Dual Voltage SD Memory Cards that can operate within the

voltage range of Low Voltage Range (T.B.D) and 2.7-3.6 V.

Note that details of Dual Voltage SD Memory Card will be defined in future specification.

3.3 Card Capacity

In terms of capacity, two types of SD Memory Cards are defined:

• Standard Capacity SD Memory Cards supports capacity up to and including 2 G bytes (2

bytes).

All versions of the Physical Specifications define the Standard Capacity SD Memory Card.

• High Capacity SD Memory Cards supports capacity more than 2 G bytes (2

bytes) and this version

of specification limits capacity up to and including 32 GB. High Capacity SD Memory Card is newly

defined from the Physical Layer Specification Version 2.00.

Only hosts that are compliant to the Physical Layer Specification version 2.00 or higher and the SD File

System Specification Ver2.00 can access High Capacity SD Memory Cards. Other hosts fail to initialize

High Capacity SD Memory Cards (See Figure 3-1).

Note:

1. The Part 1 Physical Layer Specification Version 2.00 and Part 2 File System Specification

Version 2.00 allow Standard Capacity SD Memory Cards to have capacity up to and

including 2 GB and High Capacity SD Memory Cards to have capacity up to and including

32 GB. SD Memory Cards with a capacity greater than 32 GB will be available with updated

versions of Part 1 and Part 2 Specifications.

2. Hosts that can access (read and/or write) SD Memory Cards with a capacity greater than 2

GB and up to and including 32 GB, shall also be able to access SD Memory Cards with a

capacity of 2 GB or less.

Physical Layer Simplified Specification Version 2.00

3.5 Bus Topology

This section is a blank for the Simplified Specification.

3.6 Bus Protocol

3.6.1 SD Bus

Communication over the SD bus is based on command and data bit streams that are initiated by a start

bit and terminated by a stop bit.

• Command: a command is a token that starts an operation. A command is sent from the host either

to a single card (addressed command) or to all connected cards (broadcast command). A command

is transferred serially on the CMD line.

• Response: a response is a token that is sent from an addressed card, or (synchronously) from all

connected cards, to the host as an answer to a previously received command. A response is

transferred serially on the CMD line.

• Data: data can be transferred from the card to the host or vice versa. Data is transferred via the

data lines.

Figure 3-2: “no response” and “no data” Operations

Card addressing is implemented using a session address, assigned to the card during the initialization

phase. The structure of commands, responses and data blocks is described in Chapter 4. The basic

transaction on the SD bus is the command/response transaction (refer to Figure 3-2). This type of bus

transaction transfers their information directly within the command or response structure. In addition,

some operations have a data token.

Data transfers to/from the SD Memory Card are done in blocks. Data blocks are always succeeded by

CRC bits. Single and multiple block operations are defined. Note that the Multiple Block operation mode

is better for faster write operation. A multiple block transmission is terminated when a stop command

follows on the CMD line. Data transfer can be configured by the host to use single or multiple data lines.

command response

block read operation

data stop operation

CMD

DAT

from

host

to card

stop command

stops data transfer

data from card

to host

from

card

to host

data block crc

data block crc data block crc

multiple block read operation

Figure 3-3: (Multiple) Block Read Operation

The block write operation uses a simple busy signaling of the write operation duration on the DAT0 data

line (see Figure 3-4) regardless of the number of data lines used for transferring the data.

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