【整理】嵌入式外设之SD/MMC

最后更新:2013-11-11

TODO:

1.整理SD的各种类型:

MMC
RS-MMC
MMCplus
SecureMMC
SDIO
SD
miniSD
microSD

2.以及SD本身根据速度还分:SDHC,SDXC等。


SD/MMC简介

常见的外设接口之一。

现在比较流行的手机,Android手机中,常常就支持再插入一个外接存储卡,就是SD卡。

只不过是小型接口的MicroSD。

 

SD/MMC的名称解释

之所以常常看到,把SD和MMC连在一起叫。

那是因为:

SD接口,算是MMC接口的升级版,

理论上,SD接口和更早的MMC接口是兼容的。

所以,可以看做是同样的物理上的一个接口

所以一般是把SD和MMC连在一起叫:

SD/MMC接口

 

 

SD/MMC的物理外形和接口说明

 

MMC卡长啥样

先上图,看看常见的MMC卡,是什么样的:

正面:

what looklike for common mmc card front

注:最下面那个是MMC卡的插槽

反面:

what looklike for common mmc card back

 

 

SD卡长啥样

再来看看SD卡长啥样:

common sd card looklike what

另外,还有一个小型的SD卡,叫做MicroSD,其明显小了一号

对应的可以通过普通的SD卡的卡套,变成和普通SD类似的效果:

micro sd card and adapter

 

MMC和SD卡引脚说明

直接上图:

sd mmc pins comparation

真实的SD卡和MMC卡,背面对比:

real sd vs mmc card

再加一个,带引脚说明的对比图:

sd card and mmc card pins name function

很明显:

MMC和SD,在接口上,都还是很类似,很兼容的。

对应的,SD和MMC的接口的名称和含义,

如下:

MMC卡的引脚名称和功能

对应的,MMC,分MMC模式和SPI模式,引脚和功能,不太一样:

 

MMC卡模式(MultiMedia Card mode)时的MMC引脚名称和功能

Pin Signal Description
1 RSV NC Not connected or Always ?1? (data 3?)
2 CMD I/O Command/Response
3 VSS1 S Supply Voltage Ground
4 VDD S Supply Voltage
5 CLK I Clock
6 VSS2 S Supply Voltage Ground
7 DAT0 I/O PP Data 0

 

SPI模式时的MMC引脚名称和功能

Pin Signal Description
1 CS Chip select (neg. true)
2 DI DATA in
3 Vss Ground
4 Vcc Power supply
5 SCLK Clock
6 Vss2 Ground
7 DO DATA out

 

SD卡的引脚名称和功能

SD卡,也分对应的SD模式和SPI模式

Pin SD Mode SPI Mode
Name Type Description Name Type Description
1 CD/DAT3 I/O/PP Card detection / Connector data line 3 CS I Chip selection in low status
2 CMD PP Command/Response line DI I Data input
3 Vss1 S GND VSS S GND
4 Vdd S Power supply VDD S Power supply
5 CLK I Clock SCLK I Clock
6 Vss2 S GND VSS2 S GND
7 DAT0 I/O/PP Connector data line 0 DO O/PP Data output
8 DAT1 I/O/PP Connector data line 1 RSV    
9 DAT2 I/O/PP Connector data line 2 RSV    

 

 

SD卡或MMC卡在卡Card的模式时的引脚功能说明

 

Pin No. Name Type Explanation
1 CD/DAT3 Input/Output using push pull drivers After power up this line is input with 50 kOhm pull-up. This can be used for card detection. Relevant only for SD cards, pull-up resistor is disabled after initialization procedure for using this line as DATA3 line for data transfer.
2 CMD Push Pull This is a bi-directional line. It is a bidirectional command channel used for card initialization and data transfer commands. The CMD signal has two operation modes: open-drain for initialization mode and push-pull for fast command transfer. Commands are sent from the MultiMediaCard bus master (card host controller) to the card and responses from the cards to the host.
3 Vss Power supply Supply voltage ground.
4 Vdd Power supply Supply voltage.
5 CLK Input With each cycle of this signal an one bit transfer on the command and data lines is done. The frequency may vary between zero and the maximum clock frequency.
6 Vss2 Power supply Supply voltage ground.
7 DAT[0] Input/Output using push pull driver DAT is a bidirectional data channel. The DAT signal operates in push-pull mode. Only one card or the host is driving this signal at a time. Relevant only for SD cards: On data transfer, this line is DATA 0.
8 DAT[1] Input/Output using push pull drivers On MMC card this line does not exist. Relevant only for SD cards: On data transfer, this line is DATA 1.
9 DAT[2] Input/Output using push pull drivers On MMC card this line does not exist. Relevant only for SD cards: On data transfer, this line is DATA 2.

 

SD卡或MMC卡在SPI模式时的引脚功能说明

 

Pin No. Name Type Explanation
1 CS Input Chip Select sets the card active at low level and inactive at high level.
2 Data In Input Data In is seen from the card, therefore data transmitted to the card will be received from this line.
3 Vss Supply ground Supply voltage ground.
4 Vdd Supply voltage Supply voltage.
5 SCLK Input Clock signal must be generated by the target system.
The card is always in slave mode.
6 Vss2 Supply ground Supply voltage ground.
7 Data Out Output Data Out is seen from the card. Data transferred to host will be sent by card from this line.
8 Reserved Not used
9 Reserved Not used

 

总结

SD/MMC,还是使用的很广泛的。

 

其他资料

之前收集的,供参考:

基于S3C2410的SD卡linux驱动工作原理

SD和MMC记忆卡介面技术[ZT]

High Capacity for SD Family

SD Card Specifications

和刚才参考的:

http://en.wikipedia.org/wiki/MultiMediaCard

SD-, SDHC- und MMC-Karten an AVR anschließen

How to Use MMC/SDC

MultiMedia Card (MMC) pinout

Secure Digital (SD) card pinout

Driver SD, SDHC & MMC



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