SD卡物理层规范2.0详解

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"SD规范2.0是SD卡物理层简化的版本，由SD集团（包括松下、闪迪和东芝公司）和技术委员会共同制定，旨在定义SD内存卡的物理接口、命令协议以及其使用环境和处理方式。该规格书自2006年9月25日发布，是SD卡技术的重要更新。" SD规范2.0是SD卡技术发展的一个重要里程碑，它在SD卡的物理层面上进行了改进和扩展，以满足更高的数据传输速度和容量需求。以下是对SD规范2.0中的关键知识点的详细解释： 1. 物理接口：SD规范2.0引入了新的物理接口，提高了数据传输速率。这通常涉及到更复杂的信号处理技术，如高速串行总线，可能包括更宽的数据线（例如4位或8位），以实现比前一代更快的数据传输速度。 2. 命令协议：规范中详细定义了SD卡与主机系统之间的命令交互协议。这些命令用于读取、写入数据，管理卡片状态，以及执行其他操作如初始化和错误检测。2.0版可能增加了新的命令以支持高级功能，如安全特性、多分区管理和电源管理。 3. 容量扩展：随着技术的进步，SD规范2.0可能支持更大的存储容量，这使得SD卡可以应用于高清视频、大文件存储和其他需要大量存储空间的应用。 4. 兼容性：尽管引入了新特性和功能，SD规范2.0仍保持与早期版本的兼容性，允许旧设备读取和写入新版本的SD卡，但可能无法利用所有新功能。 5. 电源管理：为了适应移动设备的低功耗需求，2.0版本可能会包含更高效的电源管理机制，包括不同工作模式下的功率优化，如休眠模式和高速模式。 6. 安全性增强：SD规范2.0可能包含了更多针对数据安全的特性，如加密技术和访问控制，以保护用户数据免受未授权访问。 7. 性能提升：除了速度提升外，SD 2.0还可能包括性能改进，例如减少延迟、提高突发传输速度等，以提升整体系统性能。 8. 工作环境：规范会定义SD卡的工作环境，包括温度范围、电压稳定性、电磁兼容性等，以确保卡片在各种条件下可靠运行。 9. 扩展功能：SD规范2.0可能还定义了一些扩展功能，如SDIO（Secure Digital Input/Output），允许SD卡不仅仅是存储设备，还能作为其他设备（如Wi-Fi模块或GPS接收器）的接口。 SD规范2.0是SD卡技术的一次重大升级，它不仅提升了速度和容量，还增强了安全性、兼容性和功能多样性，对于移动设备和嵌入式系统的发展起到了关键推动作用。

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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