Pin Details of SD, miniSD & micro SD Cards

Secure Digital (SD) Cards are digital removable flash memory cards commonly used in cell phones, digital camera , hand held GPS devices and portable media players an so on. There are three types of SD cards available depending on its size.

1. SD cards:  32x24 mm^2
2. miniSD cards :  21.5x20 mm^2
3. microSD cards:  15x11 mm^2

These memory cards are usually operated either in serial mose (SPI mode) or parallel mode (SD mode). The reading function of SD cards  is accomplished by a memory card reader that can be connected to a USB port in a computer.

A memory card reader  having a USB interface is used for accessing data on the SD card. Most card reader also offer write capability, and together with the memory card, these can function as a pendrive.

Pin Details of SD memory Cards in SD and SPI modes

Pin No.    Pin name         SD mode signal function   SPI mode signal function

1              DAT3/CS           Data line 3                         Chipselect
2              CMD/CI            Command line                     Master in/slave out
3              VSS1                 Ground                               Ground
4              Vdd                    Supply voltage 2.7/3.6V     Supply voltage 2.7/3.6V
5              CLK                  Clock                                 Clock
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

Pin Details of miniSD cards in SD and SPI modes

 Pin No.   Pin name        SD mode signal function      SPI mode signal function

1             CD/DAT3        Chip select/Data line 3            Chip select
2             CMD               Command line                         Data in (DI)
3             VSS1               Ground                                   Ground
4             Vdd                  Supply voltage 2.7/3.6V         Supply voltage 2.7/3.6V
5             CLK                 Clock                                     Clock (SCK)
6             Vss2                 Ground                                   Ground
7             DAT0               Data bit 0                                Data Out (DO)
8             DAT1               Data bit 1                                Unused
9             DAT2               Data bit 2                                Unused
10           NC                   Future use                               Future use   
11           NC                   Future use                               Future use   

Pin Details Of microSD cards in SD and SPI modes

 Pin No.  Pin name          SD mode signal function     SPI mode signal function

1             DAT2/NC          Data bit 2                              No connection
2             CD/DAT3          Card detect/Data bit 3           Chip select
3             CMD/DI            Command line                       Master out/Slave in (MOSI)
4             Vdd                    Supply voltage 2.7/3.6V        Supply voltage 2.7/3.6V
5             CLK                  Clock                                    Clock
6             Vss                    Ground                                 Ground
7             DAT/D0             Data bit 0                              Master in/slave out (MISO)
8             DAT1/RSV        Data bit 1                              Reserved

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