SD卡规范2.0详解：物理层简明规格

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"SD卡规范2.0版，包含了开发SD卡所需的所有信息。" SD卡规范，特别是2.0版本，是SD卡技术的核心文档，它定义了SD卡的物理层标准，包括尺寸、电气特性、通信协议以及与主机系统的接口。这个规范由SD卡协会（SDCardAssociation）发布，并由松下（MatsushitaElectricIndustrialCo.,Ltd.，即现在的松下电器）、闪迪（SanDiskCorporation）和东芝（ToshibaCorporation）的技术委员会共同制定。该规范的2.0版在2006年9月25日发布，相较于之前的1.10版本，它可能包含了若干重要的更新和改进。虽然具体内容未在摘要中详述，但通常SD卡规范的升级会涉及以下几个方面： 1. **速度等级**：2.0版可能会引入新的速度等级，以适应更高性能的需求，如Class10、UHS-I（Ultra High Speed Bus Interface）或UHS-II等级，确保数据传输速率的提升。 2. **容量扩展**：随着存储技术的发展，2.0版可能扩展了SD卡的最大存储容量，可能支持更大的GB甚至TB级别的存储空间。 3. **电源管理**：随着便携式设备对电池寿命的要求提高，2.0版可能强化了电源管理功能，降低了功耗。 4. **错误校验**：为了提高数据可靠性，可能会包含更强大的错误检测和纠正机制，如CRC（循环冗余校验）和ECC（错误校正码）。 5. **安全特性**：2.0版可能引入了新的安全特性，如加密技术，以保护存储在卡上的数据不被非法访问。 6. **兼容性**：新的规范会确保与旧版本的向后兼容，同时可能增加了对新设备的支持，如高清摄像机、高速多任务设备等。 7. **物理设计**：可能改进了SD卡的物理设计，使其更耐用，更适应各种环境条件，如防尘、防水、防震。 8. **新接口**：可能引入了新的接口标准，如High Speed SPI模式，以提高非主控器设备的连接速度。 SD卡规范2.0是SD卡制造商、软件开发者和系统集成商的重要参考，它确保了所有符合此规范的SD卡能在不同设备上一致工作，推动了移动存储技术的发展。通过遵循这一规范，开发者可以构建出兼容性好、性能稳定的SD卡产品，满足用户日益增长的数据存储和传输需求。

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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