Understanding Mobile Phones Removable Memory Card Pinouts - For Memory Card Problems and Failure Repair

By learning how does the removable memory card works on mobile phone devices. We can easily configure on how to repair if something went wrong when the memory card related problems such as  memory card can't be read, memory card not detected and many other related memory card errors  on mobile phones occurred.

But first, we must also understand about removable memory cards and how it is being constructed.
In mobile phones there are three types of removable memory card being used the first was the SDcard which is so big in size used on some old model cell phones and then comes the MiniSD and the latest is the microSD card which the  smaller one and commonly used in most latest designs.


Secure Digital is what SD means, it is a flash based removable memory card. The card format may also be used other device functions in addition to data storage.


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

MiniSD Card is a type of Removable NAND flash memory card format.
miniSD cards have memory capacities ranging from 256MB to 4GB. However, some of the capacity may be used for formatting and other functions, and not available for data storage. A miniSD card will fit in an SD card slot with a miniSD Adapter, miniSD Adaptes makes miniSD memory cards compatible with all SD-based devices.
There are 3 speed grades: Class 2, 2MB/s, Class 4, 4MB/s and class 6 card, 6MB/s.



The MiniSD Card measures 20mm x 21.5mm and 1.4mm thick.

miniSD Pinout Configuration
Pin # Pin Name SD Signal Function SD Mode SPI Signal Function SPI Mode
1 CD/DAT3 Chip Detect/Data Line 3 Chip Select
2 CMD Command Line Data In [DI]
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 Data Line 0 Data Out [DO]
8 DAT1 Data Line 1 Unused
9 DAT2 Data Line 2 Unused
10 NC For future use For future use
11 NC For future use For future use

microSD Card is also a type of Removable NAND-type small flash memory card format, and has a dimensions of 11mm x 15mm and 1mm thick. MicroSD is short hand for Micro-Secure Digital [Transflash].



microSD Pinout, SD Mode
Pin # Pin Name Signal Function
1 DAT2 Data Bit 2
2 CD/DAT3 Card Detect / Data Bit 3
3 CMD Command Line
4 Vdd Supply Voltage 2.7v / 3.6v
5 CLK Clock
6 Vss Ground
7 DAT0 Data Bit 0
8 DAT1 Data Bit 1


microSD Pinout, SPI Mode
Pin # Pin Name Signal Function
1 NC No Connect
2 /CS Chip Select
3 DI Master Out/Slave In (MOSI)
4 Vdd Supply Voltage 2.7v / 3.6v
5 CLK Clock
6 Vss Ground
7 DO Master In/Slave Out (MISO)
8 RSV Reserved


Mobile phones manufacturers used  SD mode and SPI mode Memory card Signal Function, it  only varies according on mobile phones designed.  You can easily determine which one is SD mode or SPI mode designed. Just figure out the MMC slot socket then count the corresponding pins on it. In SD mode all pins has a connections while in SPI mode some of the pins are reserved and not in used or have no connection in the circuit.

In continuation of this post by learning how the Removable Memory Card Circuit works on mobile phones, and How to troubleshoot and repair memory card problem issues, we can configure which particular mobile phone used the SD mode and SPI Mode signal functions.

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