microSD
| Storage medium microSD
|
|
 Front and back of a microSD card |
|
| General | |
|---|---|
| Type | Memory card , semiconductor memory |
| capacity | microSD: 8 MB to 2 GB microSDHC: 4 GB to 32 GB microSDXC: 32 GB to 2 TB |
| size | 11.0 mm × 15.0 mm × 0.7 mm |
| use | mobile devices, etc. a. MP3 players , cell phones , netbooks, etc. |
| origin | |
| developer | SanDisk , SD Card Association (SDA) |
| idea | 2005 |
microSD (until 2005 Trans Flash ) is a very compact Flash - memory card format , the electrically with SD Memory Cards compatible. The microSDHC extension defines capacities of up to 32 GB and microSDXC up to 2 TB. Like the SD card, the microSD is licensed by the SD Association according to certain standards.
properties
With the dimensions 11 mm × 15 mm × 0.7 mm, microSD cards are very compact and light (0.25 g). They are available in capacities from 8 MB to 2 GB.
Since microSD cards are essentially a miniaturized SD memory card , the same electrical specifications apply to them. Analogous to SDHC, there are also microSDHC cards with capacities from 4 GB to 32 GB, and analogous to SDXC there are also microSDXC cards with capacities from 32 GB to currently 1 TB.
microSD cards also contain hardware functions for DRM , which prevent unauthorized playback of protected media.
history
The microSD format was originally developed by the SanDisk company under the name T-Flash (TF card), then TransFlash . When accepted by the SD Card Association (SDA), a union of Panasonic ( Matsushita ), SanDisk and Toshiba , it was finally renamed microSD in July 2005 .
application
Due to their small dimensions and their low weight, microSD cards are used in particular in mobile devices such as cell phones . Their use depends on the increasing storage requirements of cell phones and smartphones. With microSD cards, it is no longer a problem to save a large amount of photos, videos or even e-mails on a mobile phone.
Speed classes and application in cell phones
The following speed classes are defined:
- Class 2: 16 Mbit / s sequential reading ( 2 MB / s sequential writing)
- Class 4: 32 Mbit / s sequential reading ( 4 MB / s sequential writing)
- Class 6: 48 Mbit / s sequential reading ( 6 MB / s sequential writing)
- Class 10: 80 Mbit / s sequential reading (10 MB / s sequential writing)
There is also "UHS Speed Class" and "Video Speed Class", which support even higher speeds.
The classes indicate the read and write speeds for sequential access to the memory (Sequential R / W speed). However, the read and write speeds in the event of random access to the memory (Random R / W speed) are also important. Memory cards with a high sequential read speed have a slower random access speed . In order to ensure a high sequential speed of the Class 6/10 cards, the area of the memory to be read or written is initialized beforehand. This takes more time at the beginning of data access and is therefore at the expense of the speed with random access.
Application class 6/10
These cards have a higher sequential write and read rate. This is particularly important when large amounts of data are transferred to the memory card, e.g. For example, you can record HD quality videos, access albums with high-resolution photos, and copy very large files.
Application class 2/4
These cards usually have a higher speed with random access . This is important when the functions of the operating system (loading system or application files) and applications (apps) are outsourced to the memory card (App2SD).
Security applications
With the smartSD standard, the microSD card enables special additional functions, such as encryption and authentication. The SDA has created its own product category for secure memory cards that can integrate a secure element such as a smart card. The communication between host and smartSD takes place according to the ASSD standard, which is also standardized by the SDA. Typical applications are government cryptography such as crypto cell phones in government agencies.
compatibility
Other flash memory card formats recognized by the SDA are miniSD and SD . Like miniSD cards, microSD cards can be used in SD-compatible devices via a mechanical adapter. These adapters are often already included in the scope of delivery. microSDHC devices can also read microSD cards; conversely, older microSD devices are not compatible with microSDHC. There are now even microSDXC cards with at least 64 GB of memory. These are electrically compatible with microSDHC, but the microSDXC standard requires the exFAT file system , which in many cases is not supported by devices that are not microSDXC compatible. Since the FAT32 file system used in accordance with the standard also supports partition sizes of up to 8 TiB for SDHC , it is often possible to format a microSDXC card with FAT32 and thus only use it in microSDHC-compatible devices. However, only cards up to 32 GB are specified in the microSDHC standard, so there is no guarantee that a microSDXC card reformatted in this way will be recognized error-free and with full capacity in a device that only supports microSDHC.
The readers, on the other hand, are always downward compatible, i. H. a microSDXC reader can also read and write to microSDHC and microSD cards.
Terminal assignment
With the microSD card, a ground connection is saved compared to the normal SD card .
- SD mode
| Pin code | abbreviation | function |
|---|---|---|
| 1 | Dat2 | Data line bit 2 |
| 2 | Dat3 | Card Detect / data line bit 3 |
| 3 | CMD | Command line |
| 4th | Vdd | Supply voltage 2.7-3.6 V. |
| 5 | Clk | Clock input (clock) |
| 6th | GND | Signal ground |
| 7th | Dat0 | Data line bit 0 |
| 8th | Dat1 | Data line bit 1 |
- Terminal assignment in SPI mode , if implemented
| Pin code | abbreviation | function |
|---|---|---|
| 1 | Unused | not used |
| 2 | CS | Chip Select (SPI-SS Slave Select) |
| 3 | DataIn | Data input (SPI-MOSI Data Input) |
| 4th | Vdd | Supply voltage 2.7-3.6 V. |
| 5 | Clk | Clock input (clock) |
| 6th | GND | Signal ground |
| 7th | DataOut | Data output (SPI-MISO data output) |
| 8th | Unused | not used |
Web links
- SanDisk microSD / TransFlash Cards (English) - manufacturer's website with further information
- SD Card Association (en.)
- PhysOrg article on SanDisk 512MB microSD card (English)
- Samsung press release about 32 GB microSD (en.) - manufacturer's website with further information
- Sandisk announces microSDXC card
- smartSD standard - memory cards with security function (en.)
- Spiegel article on the Merkel telephone with smartSD
Individual evidence
- ↑ a b SanDisk Extreme® microSDXC ™ UHS-I memory card. In: sandisk.com. SanDisk Corporation, accessed May 11, 2020 .
- ↑ SD Memory Card - History of the SD card. In: cyberport.de. Retrieved May 11, 2020 .
- ↑ a b c d e Speed Class Standards for Video Recording - SD Speed Class. In: sdcard.org. SD Association, accessed May 11, 2020 .