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.
| 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.
| 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].
| 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 |
| 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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