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], labeled 0 to 8 as shown below.
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, which are different physical versions of the SDcard.
SDXC memory card format; XC - for 'eXtended Capacity'
Refer here for the SD Association ... http://www.sdcard.org/developers/tech/sdhc/
The format used Microsoft's exFAT [FAT 64] file system [however this site does not cover any software OS].
exFAT was introduced with Windows CE 6.0, and appeared in Vista in Service Pack 1.
Read and Write speeds to 104MB/s with 2TB capacity.
SDIO and SDHC, may be updated to support the higher data throughput.
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.
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 |
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 below [Flash Memory Stick Formats].
Refer to the Personal Computer Buses page
for more information for different memory types, as listed here.
The graphic to the right shows: Note that pin contacts 3 and pin 4 The MicroSD form factors picture [left] Article on Designing with SD Card, learn more. |
Comparison of SD Memory Card sizes SD Card, miniSD Card, microSD Card |
Acronyms; Smartmedia Host Controller (SMHC), Secured Digital Host Controller (SDHC)
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