SD卡2.0协议详解：容量升级与CMD8命令支持

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SD卡2.0协议是SD规格的一部分，它于2006年9月25日发布，由SD协会成员Matsushita Electric Industrial Co., Ltd.（松下）、SanDisk Corporation和Toshiba Corporation共同制定。相比于1.0版本，2.0协议引入了多项关键改进和扩展，主要体现在以下几个方面： 1. 容量计算优化：2.0协议对容量的定义和计算方法进行了更新，使得在更大容量的卡片支持下，能更准确地报告存储空间。这对于设备制造商和用户来说，意味着可以更好地理解和管理大容量SD卡的实际可用空间。 2. CMD8命令支持：CMD8（Command Management）命令是SD卡2.0新增的重要功能，允许设备执行高级管理操作，如固件更新、安全设置等。这增强了SD卡的可升级性和安全性，使得卡片能够适应不断发展的技术需求。 3. 简化版规范：文档名为"Physical Layer Simplified Specification Version 2.00"，表明这份指南是针对物理层的简化版本，旨在提供易于理解的接口描述，以便开发者能快速接入和开发SD卡驱动程序。 4. 修订历史：文档提供了从1.10到2.00版本的修订记录，反映了随着时间的推移，技术不断进步，协议也在不断更新和完善，确保兼容性和性能的提升。 5. 发布和版权信息：SD Card Association是该规范的主要出版者，提供了联系信息，包括电话、传真和电子邮件地址。版权归属SD Group及其成员公司，强调了合作与共享知识产权的重要性。 SD卡2.0协议作为一项关键的技术规范，对于任何涉及SD卡应用的开发者而言，了解和遵循这些变化至关重要，因为它们直接影响着设备的兼容性、性能和用户体验。无论是硬件制造商还是软件开发者，掌握这个版本的协议都是实现高效、稳定和安全SD卡交互的基础。

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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