Delkin Blog

Understanding the SD Card Interface

 

Secure Digital cards, or SD cards, are widely used in consumer and industrial markets. The SD card interface is simple and widely compatible, making it an easy choice for designers and OEMs. The Secure Digital Association determines the design specifications, and these specs are available only to members of the group. For members, the exact design protocols of the physical interface can be downloaded, which can be helpful to OEMs who are implementing SD cards into their systems. SD cards are available in both SLC NAND flash industrial formats and commercial MLC NAND flash designs. Here is what you need to know about the SD card interface.

 

Intelligent Controller

The flash management operations in SD cards are handled by an intelligent controller, and data transfers occur serially in 512-byte blocks between the host system and the card. For cards with capacities of 2Gbytes or lower, the defined file system is FAT12/16. Cards with capacities of 4Gbytes or more use FAT32.

 

This is just like CF and PC cards, which are familiar to many OEMs. However, the pinout for SD cards is different than with those designs. SD cards use nine contact pads instead of pins for contact. For legacy compatibility with MMC cards, the 9-pad is placed below the 1-pad and is positioned out of alignment and with a greater width. From top to bottom, the pinout looks like this:

8: DAT1

7: DAT0/DO

6: Vss2

5: CLK

4: Vcc

3: Vss1

2: CMD/DI

1: DAT3/CS

9: DAT2

 

Voltages

Although lower voltages are available, the standard voltage range of SD cards is 2.7-3.3V. The lower voltage models are generally designed specifically for consumer electronic devices that require this kind of reduced voltage range. Standard voltages are used for industrial grade SD cards.

 

Bus Information

SD cards operate with a default bus protocol of SD mode. However, if a simpler or slower bus is needed, the card can be configured for SPI mode. While in SPI mode, SD cards operate in one-bit bus widths. In SD mode, the cards use a serial clock mode for bus widths of between one and four bits.

 

When the SD card is put into SD or SPI mode, it cannot be switched to the other mode while power is applied. However, the modes can be switched during a power cycle as needed.

 

Delkin’s product team can answer all of your questions about the SD card interface and other industrial grade embedded storage options. Contact us today for more information or to request an engineering sample.

 

Contact

  • This field is for validation purposes and should be left unchanged.

Related Posts

Temperature Considerations for SSD- Hot Climate
The Benefits of Industrial Temperature for Industrial Applications

  Flash storage solutions come in two categories—commercial and industrial. These two product grades are...

Digital Gaming Applications
Industrial CompactFlash (CF) Cards: The Perfect Fit for Gaming Applications

  Behind the bright lights and ringing sounds of casinos are the flash storage cards...

A Case Study in Application Design That Considers Technological Advancements

  When designing state-of-the-art technological applications, designers and engineers are faced with a major challenge—creating...

Healthcare Industrial Flash Storage
Modernize Your Healthcare Data Storage with Industrial Flash

  The healthcare community relies heavily on tech for daily functions, from reading test results...

Delkin Industrial Application Lifecycle Management
Product Life Cycle Management FAQs

  When it comes to flash storage, developing a world-class application isn’t enough. Life cycle...

Person on laptop evaluating SMART data
Customer Success Story: Enhance Embedded Memory with SMART Cards

Flash storage offers a modernized opportunity to store and access data at a high...

Ruggedized SSDs- Technology for Industrial Users: What You Need to Know

  SSDs are so ubiquitous today that you may be surprised to learn that they...

Delkin Devices Technical Support: We’re Here to Help

  Delkin Devices is a global industrial Flash memory and storage provider with the best...

Power Fail
Understanding Power Failures in Flash Storage

  The Cost of Power Failures  For industrial applications, the cost of power failures can be...

Ruggedized SSDs- Technology for Industrial Users: What You Need to Know

  SSDs are so ubiquitous today that you may be surprised to learn that they...