SD Flash Card Info:


Secure Digital Card, Pin Out

Secure Digital [SD] is a flash based removable memory card. The card format may also be used other device functions in addition to data storage. Secure Digital uses a 9-Pin connector [1 rows of 9 pins]. A compatible card format is called Secure Digital I/O [SDIO]. Refer to the SDIO page for information on that card standard.
Also refer to the microSD Card, or the miniSD Card pages.


Secure Digital Card

The Secure Digital card dimensions are: 24mm wide x 32mm long. The standard width is 2.1mm, while the Thin SD Memory Card has a width 1.4mm.

Secure Digital Pinout
Pin # Pin Name SD Signal Function SD Mode SPI Signal Function SPI Mode
1 DAT3/CS Data Line 3 Chip Select/Slave Select [SS]
2 CMD/DI Command Line Master Out/Slave In [MOSI]
3 VSS1 Ground Ground
4 Vdd Voltage Supply [2.7v or 3.6v] Voltage Supply [2.7v or 3.6v]
5 Clock Clock Clock [SCK]
6 Vss2 Ground Ground
7 DAT0/D0 Data Line 0 Master In Slave Out [MISO]
8 DAT1/IRQ Data Line 1 Unused or IRQ
9 DAT2/NC Data Line 2 Unused

 

How to use a SD card.

The graphic below provides a comparison of the different Removable memory Card standards. Many of the different Memory Card standards have descriptions listed on this web site. The different standards based on card size are provided. Refer to the Personal Computer Buses page for more information for different memory types, as listed here.

Memory Board Dimension

Refer to this page for a list of different Flash Memory Stick Formats.

Wikipedia on SD cards


The graphic to the right shows:
The SD card, 32mm x 24mm
The miniSD card, 21.5 x 20mm
The microSD card, 15mm x 11mm

Note that pin contacts 3 and pin 4
are bit bit longer than the other pins.
This allows pin 3 [Vss], and pin 4 [Vdd]
to make contact in the socket before the other pins.
Allowing Ground and power to be connected first
to the SD socket.
Pins CLK, CMC, DAT0, DAT1, DAT2, and Vss
make connection after pins 3 and 4 make contact.
Pin 1, DAT3 makes contact last.
Of course pins 3 and 4 are also the last
pins to loss contact with the socket.

The MicroSD form factors picture [left]
is used under GNU License

 SD Card Sizes
Comparison of SD Memory Card sizes
SD Card, miniSD Card, microSD Card