Secure Digital

src: mcsteveonline.com

Secure Digital ( SD ) is a non-volatile memory card format developed by SD Card Association (SDA) for use in portable devices.

This standard was introduced in August 1999 by a joint effort between SanDisk, Panasonic (Matsushita Electric) and Toshiba as an improvement over MultiMediaCards (MMC), and has become an industry standard. These three companies formed SD-3C, LLC, a company licensing and enforcing intellectual property rights associated with SD and SD memory cards hosted and additional products.

The companies also established the SD Association (SDA), a non-profit organization, in January 2000 to promote and make SD Card standards. SDA currently has about 1,000 member companies. SDA uses some trademark logos owned and licensed by SD-3C to enforce compliance with its specifications and ensure user compatibility.

Video Secure Digital

Overview

Secure Digital includes four family cards available in three different sizes. The four families are Standard-Capacity (SDSC), High-Capacity (SDHC), eXtended-Capacity (SDXC), and SDIO, which combine input/output functions with data storage. Three form factors are original size, mini size, and micro size. The electric passive adapter allows smaller cards to fit and work in devices built for larger cards. The small footprint of SD cards is an ideal storage medium for smaller, thinner and more portable electronic devices.

SD (SDSC)

Second generation Secure Digital (SDSC or Secure Digital Standard Capacity) cards are developed to improve the standard MultiMediaCard (MMC), which continues to grow, but in different directions. Secure Digital changes the MMC design in several ways:

• The asymmetrical shape of the SD card side prevents it from tipping in reverse (while the MMC enters most of the way but makes no contact if it is reversed).
• Most SD cards have a thickness of 2.1 mm (0.083 inches), compared to 1.4 mm (0.055 inches) for the MMC. The SD specification defines a card called Thin SD with a thickness of 1.4 mm, but is rare, since SDA continues to determine smaller form factors.
• The card's electrical contacts are hidden beneath the card surface, protecting them from contact with the user's finger.
• The SD specification envisions capacities and transfer rates beyond the MMC, and both of these functions have evolved over time. For comparison table, see below.
• While the MMC uses a single pin for data transfer, the SD card adds a four-wire bus mode for higher data rates.
• The SD card adds Content protection for Media Record security circuits (CPRM) for digital rights management (DRM) content protection.
• Additional notch writing

The full size SD card does not match the slender MMC slot, and other issues also affect the ability to use one format in a host device designed for another.

SDHC

The Secure Digital High Capacity (SDHC) format, announced in January 2006 and defined in version 2.0 of the SD specification, supports cards with capacities up to 32 GB. Trademarks SDHC is licensed to ensure compatibility.

The SDHC card is physically and electrically identical to a standard SD (SDSC) card. The main compatibility issue between SDHC and SDSC cards is the redefinition of Data-Specific Data registers (CSD) in version 2.0 (see below), and the fact that SDHC cards are shipped are preformatted with the FAT32 file system.

Version 2.0 also introduced high-speed bus modes for SDSC and SDHC cards, which doubled the Standard Speed ​​clock to produce 25 MB/s.

The SDHC host device is required to accept an older SD card. However, older host devices do not recognize SDHC or SDXC memory cards, though some devices may do so through upgrading the firmware. Old Windows operating systems released before Windows 7 require patches or service packs to support access to SDHC cards.

SDXC

The eXtended Capacity Secure Digital (SDXC) format, announced in January 2009 and defined in version 3.01 of the SD specification, supports cards up to 2Ã, TB (2048Ã, GB), compared to the 32Ã, GB limit for SDHC cards in the SD 2.0 specification. SDXC adopts Microsoft's exFAT file system as a mandatory feature.

Version 3.01 also introduced Ultra High Speed ​​bus (UHS) for SDHC and SDXC cards, with interface speeds of 50 MB/sec up to 104 MB/sec for four-bit UHS-I bus.

Version 4.0, introduced in June 2011, allows speeds of 156Ã, MB/s up to 312Ã, MB/dt through the UHS-II four-lane (two-lane differential) bus, requiring additional rows of physical pins.

Version 5.0 was announced in February 2016 in CP 2016, and added a "Video Speed ​​Class" rating for UHS cards to handle high resolution video formats like 8K. The new rating determines the minimum write speed of 90 MB/sec.

exFAT filesystem

The SDXC card utilizes the exFAT file system, its use is governed by a proprietary license, thus limiting its legal availability to a small set of operating systems. Therefore, an ExFAT formatted SDXC card is not a universally readable exchange medium.

Windows Vista (SP1) and later and OS X (10.6.5 and later) support exFAT out of the box. (Windows XP and Server 2003 can support exFAT via optional updates from Microsoft.) Most BSD and Linux distributions do not, for legal reasons; users must manually install third-party exFAT implementations (as FUSE modules) in order to mount exFAT-formatted volumes. However, SDXC cards can be reformatted to use any file system (such as ext2, UFS, or VFAT), reducing the restrictions associated with the availability of exFAT.

However, in order to fully comply with the SDXC card specifications, many SDXC-enabled device devices are programmed-firmware to expect exFAT on cards larger than 32 GB. As a result, they may not accept SDXC cards that are reformatted as FAT32, even if the device supports FAT32 on a smaller card (for SDHC compatibility). Therefore, even if the file system is generally supported, it is not always possible to use an alternate file system on an SDXC card at all depending on how strictly SDXC card specifications have been applied to the host device. It assumes the risk of accidental data loss, because the host device can treat the card with an unrecognized file system as empty or damaged and reformat the card.

SD Association provides formatting utilities for Windows and Mac OS X that check and format SD, SDHC, and SDXC cards.

Ultra High Speed ​​Bus (UHS)

Ultra High Speed ​​Bus (UHS) is available on some SDHC and SDXC cards. The following ultra-high speeds are determined:

UHS-I

Specified in SD 3.01 version,

Supports clock frequencies of 100Ã ¢, MHz (four times the original "Default Speed"), which in four-bit transfer mode can transfer 50 Ã, MB/s (SDR50). The UHS-I card stated as UHS104 (SDR104) also supports clock frequency of 208 MHz, which can transfer 104 MB/sec. Double data rate operations at 50 MHz (DDR50) are also specified in Version 3.01, and are required for microSDHC and microSDXC cards labeled UHS-I. In this mode, four bits are transferred when the clock signal rises and four other bits when it falls, transferring the entire byte in every full clock cycle, then the 50 MB/s operation can be transferred using the 50 MHz clock.

UHS-II

Specified in version 4.0, further raising the data transfer rate to a theoretical maximum of 156 MB/s (full duplex) or 312 MB/s (half duplex) using additional pin lines (17 pins total for full size and 16 pin for micro size card).

UHS-III

Version 6.0, released in February 2017, added two new data rates to the standard. FD312 provides 312 MB/sec while FD624 doubles it. Both are full duplex. The physical interface and pin layout are the same as UHS-II, maintaining backward compatibility.

A card corresponding to UHS shows the Roman numerals 'I', 'II' or 'III' next to the SD card logo, and reports this ability to the host device. UHS-I usage requires that the host device instructs the card to drop from 3.3 volts to a 1.8 volt operation via the I/O interface pin and choose a four-bit transfer mode, while UHS-II requires 0.4 volt operation.

Higher speed rates are achieved by using a low two-lane differential interface (0.4 V pp). Each channel is capable of transfering up to 156 MB/s. In full duplex mode, one path is used for Transmit while the other is used for Receive. In half duplex mode both paths are used for same data transfer directions allowing multiple data rates at the same clock speed. In addition to allowing higher data rates, the UHS-II interface allows lower power consumption interfaces, lower I/O voltages, and lower electromagnetic interference (EMI).

Maps Secure Digital

Speed ​​

The speed of the SD card is usually judged by the read or write sequential speed. The sequential performance aspect is the most relevant for storing and retrieving large files (relative to block internal size to flash memory), such as images and multimedia. Small data (such as file name, size and time stamp) are below the much lower speed limit of random access, which can be a limiting factor in some use cases.

With the initial SD card, some card manufacturers set the speed as "times" ("ÃÆ'â €") rating, which compares the average speed of reading data to those on the original CD-ROM drive. This is replaced by Fast Class Rating , which ensures the minimum level at which data can be written to the card.

Newer families of SD cards improve card speed by increasing the bus rate (the clock signal frequency that plugs in and out of card information). Regardless of the bus fare, the card can signal to the host that it is "busy" until the read or write operation is complete. Compliance with a higher speed rating is a guarantee that the card limits its use for "busy" indications.

Speed ​​class rating

SD Association defines a standard speed class for SDHC/SDXC cards that show minimum performance (minimum serial data writing speed). Read and write speeds must exceed the specified values. The specification defines these classes in terms of performance curves that translate into the following minimum read-write performance levels on blank cards and suitability for different applications:

The speed classes 2, 4, and 6 state that the card supports the number of megabytes per second as the minimum continuous write speed for cards in a fragmented state. Class 10 confirms that the card supports 10Ã, MB/s as a minimum non-fragmented sequential writing speed and uses High Speed ​​bus mode. The host device can read the speed class of the card and alert the user if the card reports a speed class that falls below the minimum requirement of the application. In comparison, the older "ÃÆ'â €" rating measures the maximum speed under ideal conditions, and it is not clear whether the read or write speed is read. The graphic symbol for the speed class has a number encircled with 'C' (C2, C4, C6, and C10).

UHS-I and UHS-II cards can use the UHS Speed ​​Class rating with two possible values: class 1 for read/write performance of at least 10 MB/s (symbol 'U1 'which displays the number 1 in' U ') and grade 3 for a write performance of at least 30 MB/s (' U3 'symbol featuring 3 in' U '), targeted to record 4K video. Prior to November 2013, the rating was labeled UHS Speed ​​â € <â € and contained a value of 0 (without symbol) and 1 (symbol 'U1'). Manufacturers can also display standard speed class symbols (C2, C4, C6, and C10) in addition to, or in place of UHS speed class.

Video Speed ​​Class defines a set of requirements for UHS cards to match modern MAND flash memory and support 4K and progressive 8K video with a minimum sequential writing speed of 6-90 MB/s. Graphic symbols using 'V' followed by a number indicating write speed (V6, V10, V30, V60, and V90).

The Performance Class App is the newly defined standard of SD Specifications 5.1 and 6.0 which not only specify a sequential Reading Speed ​​but also mandate minimum IOPS for read and write. Class A1 requires a minimum of 1500 reads and 500 write operations per second, while A2 class requires 4000 and 2000 IOPS.

UHS memory cards work best with UHS host devices. This combination allows users to record HD resolution video with camcorder without filter while performing other functions. It's also suitable for real-time broadcasting and capturing great HD videos.

The most important suggestion for consumers is to keep matching SD card purchases to the recommended speed class of apps. Apps that require a particular speed class usually specify this in their user manual.

"ÃÆ'â €" "rated

The "ÃÆ'â €" rating, used by some card manufacturers and made obsolete by the speed classes, is a multiple of the 150 KiB/s standard CD-ROM drive speed (about 1.23 Mbit/sec). Basic card transfers data up to six times (6ÃÆ'â € ") CD-ROM speed; ie, 900BB/s or 7.37 Mbit/s. The 2.0 specification defines speeds up to 200ÃÆ'â € ", but is not as specific as Speed ​​Class on how to measure speed. Manufacturers can report the best speed and can report the fastest read speed of the card, which is usually faster than write speed. Several vendors, including Transcend and Kingston, reported the speed of writing their cards. When a card includes a speed class and a "ÃÆ'â €" rating, the latter may be assumed to have read speed only.

Real-world performance

In applications requiring continuous write throughput, such as video recording, the device may not function satisfactorily if the SD card rating falls below a certain speed. For example, high-definition camcorders may require cards no less than Class 6, suffer dropouts or video breaks if cards are slower to use. A digital camera with a slow card may take some time after taking a photo before it is ready for the next, while the camera writes the first image.

The speed class rating does not fully describe the card's performance. Different cards of the same class can vary greatly when they meet the class specifications. Card speed depends on many factors, including:

• The number of soft errors that the card controller should try again
• Amplify write: Flash controllers may need to overwrite more data than requested. This has something to do with the read-write operation on the write block, freeing the eraser block (which is much larger), while moving the data around to achieve level wear.
• File fragmentation: if there is not enough space for the file to be recorded in the adjacent region, this file is divided into non-contiguous fragments. This does not cause rotational or head-movement delays like on an electromechanical hard drive, but can decrease speed; for example, by requiring additional readings and calculations to determine where on the card, the next fragment of the file is stored.

In addition, the speed can vary greatly between writing large amounts of data to a single file (sequential access, such as when a digital camera is recording a large photo or video) and writing a large number of small files (the use of common random access on a smartphone). A study in 2012 found that, in the use of this random access, some Class 2 cards achieved write speeds of 1.38 MB/s, while all the cards tested Class 6 or greater (and some lower Class; Lower classes are not always means better file performance), including those from large manufacturers, more than 100 times slower. In 2014, a blogger measures a 300-fold performance difference in small writing; this time, the best card in this category is a 4th grade card.

src: static.shoplightspeed.com

Features

Card security

Cards can protect their content from deletion or modification, prevent unauthorized user access, and protect copyrighted content using digital rights management.

Command to disable writing

The host device can instruct the SD card to be read-only (to reject the next command to write information to it). There are both reversible and irreversible host commands that achieve this.

notepad-protect

Users can designate most full size SD cards as read-only by using a sliding tab that covers the notches on the card. The miniSD and microSD formats do not support write protection notch.

When looking at the SD card from above, the right side (side with oblique angle) should be curved.

On the left side, there may be a curve of write protection. If the notch is removed, the card can be read and written. If the card is hollow, it is read-only. If the card has a notch and a sliding tab covering the notch, the user can slide the tab up (towards the contact) to declare the read/write card, or down to indicate read-only. The diagram on the right shows an orange sliding write-protect tab in both locked and locked positions.

The presence of a notch, and the presence and position of the tab, has no effect on SD card operations. Host devices that support write protection should refuse to write to a read-only SD card in this way. Some host devices do not support write protection, which is an optional feature of the SD specification. Drivers and devices that comply with read-only indications may give users a way to override them.

Cards that are sold with content that should not be permanently changed are marked read-only by having notches and no sliding tabs.

Card password

The host device can lock the SD card using a password up to 16 bytes, usually supplied by the user. The locked card interacts normally with the host device except that it rejects the command to read and write data. Locked cards can only be opened by providing the same password. The host device can, after entering the old password, specifying a new password or disabling the lock. Without a password (usually, in the case that the user forgets the password), the host device may order the card to delete all data on the card for future use (except card data under DRM), but there is no way to gain access to data which exists.

Windows Phone 8 devices use SD cards designed for access only by phone manufacturers or mobile operators. The SD card inserted into the phone under the battery compartment becomes locked "to the phone with auto-generated key" so that "SD card can not be read by phone, device, or other PC". Symbian devices, however, are some of the few that can perform low level format operations required on a locked SD card. It is therefore possible to use devices such as Nokia N8 to reformat the card for subsequent use on other devices.

smartphs smarts card

The smartSD memory card is a microSD card with an internal "secure element" that enables the transfer of ISO 7816 Protocol Unit Data commands to, for example, JavaCard applets running on internal secure elements via the SD bus.

Various smartSD card implementations have been made for secure payment and authentication applications.

microSD cards with Secure Element and NFC (close field communications) are used for secure payments and access.

Device enhancement

Vendors try to differentiate their products in the market through vendor-specific features:

• Integrated Wi-Fi - Some companies produce SD cards with internal Wi-Fi transceivers that support static security (WEP 40; 104; and 128, WPA-PSK, and WPA2- PSK ). This card allows any digital camera with an SD slot to transmit images captured over the wireless network, or store images on the card memory until it is within wireless network coverage. Examples include: Eye-Fi/SanDisk, Transcend Wi-Fi, Toshiba FlashAir, Flucard Tracks, PQI Water Card, and LZeal ez Share. Some models geotag their images.
• Pre-loaded content - In 2006, SanDisk announced Gruvi, a microSD card with additional digital rights management features, which they refer to as a medium for publishing content. SanDisk again announced a pre-loaded card in 2008, under the slotMusic name, this time not using any of the DRM capabilities of the SD card. In 2011, SanDisk offers a wide collection of 1000 songs on a single slotMusic card for around $ 40, now limited to compatible devices and without the ability to copy files.
• Integrated USB connectors - SanDisk products SD Plus can be plugged directly into a USB port without the need for a USB card reader. Other companies introduced comparable products, such as the Duo SD product from OCZ Technology and the 3 Way (microSDHC, SDHC and USB) product from A-DATA, available in 2008 only.
• Different colors - SanDisk has used a variety of plastic or adhesive label colors, including the "game" line in transparent plastic colors that indicate the capacity of the card.
• Integrated view - In 2006, A-DATA announced a Super SD card with a digital display that labeled two characters and showed the amount of unused memory on the card.

SDIO card

The SDIO (Secure Digital Input Output) SD card is an extension of the SD specification to include I/O functions. SDIO cards work only fully in host devices designed to support their input-output functions (usually PDAs such as Palm Treo, but sometimes laptops or phones ). This device can use SD slot to support GPS receiver, modem, barcode reader, FM radio tuner, TV tuner, RFID reader, digital camera and interface to Wi-Fi, Bluetooth, Ethernet and IrDA. Many other SDIO devices have been proposed, but it is now more common for I/O devices to connect using the USB interface.

The SDIO card supports most of the SD card memory commands. SDIO cards can be arranged as eight logical cards, although currently, the typical way that SDIO cards use this capability is to structure itself as one I/O card and one memory card.

The SDIO and SD interfaces are mechanically and electrically identical. Host devices built for SDIO cards generally accept SD memory cards without I/O functionality. However, the opposite is not true, because the host device requires the appropriate drivers and applications to support I/O card functions. For example, an HP SDIO camera usually does not work with a PDA that does not list it as an accessory. Inserting an SDIO card into any SD slot does not cause physical damage or disruption to the host device, but users may be frustrated because the SDIO card is not fully functional when it is inserted into a seemingly compatible slot. (USB and Bluetooth devices show comparable compatibility issues, albeit at a lower level thanks to the standard USB device class and Bluetooth profile.)

The SDIO family consists of Low Speed ​​and Full Speed ​​cards. Both types of SDIO cards support SPI and single-bit SD bus types. SDIO Low Speed ​​Card is allowed to also support four-bit SD bus; Full-Speed ​​SDIO Card â € <â €

Merge a shared card

The one-bit SD protocol is derived from the MMC protocol, which envisages the ability to store up to three cards on a common signal path bus. The card uses an open collector interface, where cards can draw lines to low voltage levels; the line is at a high voltage level (due to the pull-up resistor) if no card draws it low. Despite the card sharing hours and signal lines, each card has its own chip select line to sense that the host device has selected it.

The SD protocol envisions the ability to raise 30 cards together without a separate chip select line. The host device will broadcast commands to all cards and identify cards to respond to commands using a unique serial number.

In practice, cards are rarely united because open collector operations have problems at high speed and increase power consumption. The new version of the SD specification recommends separate lines for each card.

Compatibility

Host devices that conform to the newer version specifications provide backward compatibility and accept older SD cards. For example, the SDXC host device receives all previous families from the SD memory card, and the SDHC host device also accepts standard SD cards.

Older host devices generally do not support newer card formats, and even when they may support the bus interface used by the card, there are several factors that arise:

• Newer cards may offer greater capacity than the host device can handle (more than 4 GB for SDHC, more than 32 GB for SDXC).
• The newer card can use a file system that can not be navigated by the host device (FAT32 for SDHC, exFAT for SDXC)
• The use of the SDIO card requires a host device designed for the card-supplied input/output function.
• The card hardware interface is changed starting with version 2.0 (new high-speed bus clock, redefined from bit storage) and SDHC (Ultra-high speed (UHS)) family
• UHS-II has a more physical pin but is compatible with UHS-I and non-UHS for slots and cards.
• Some vendors produce SDSC cards above 1GB before SDA has a standard method for doing so.

src: www.schillers.com

History

In 1999, SanDisk, Matsushita, and Toshiba agreed to develop and market Secure Digital (SD) Memory Cards. This card comes from MultiMediaCard (MMC) and provides digital rights management based on Secure Digital Music Initiative (SDMI) standards and for high time, memory density.

It's designed to compete with Memory Stick, a DRM product released by Sony the previous year. Developers predict that DRM will encourage widespread use by music suppliers who worry about piracy.

The trademarked SD logo was originally developed for the Super Density Disc, which was a Toshiba entry that was not successful in the DVD format war. For this reason, D in the logo resembles an optical disc.

At the Consumer Electronics Show (CES) trade show 2000, the three companies announced the establishment of SD Association (SDA) to promote SD cards. The SD Association, headquartered in San Ramon, California, USA, started with about 30 companies and currently consists of about 1,000 product manufacturers that make memory cards and interoperable devices. Initial SD Card samples became available in the first quarter of 2000, with production numbers of 32 and 64 MB cards available three months later.

Mini and micro cards

The miniSD form was introduced in March 2003, CeBIT by SanDisk Corporation announcing and demonstrating it. The SDA adopted a miniSD card in 2003 as a small form factor extension to an SD card standard. While new cards are specially designed for mobile phones, they are usually packed with miniSD adapters that provide compatibility with standard SD memory card slots.

In September 2006, SanDisk announced a 4 GB miniSDHC. Like SD and SDHC, the miniSDHC card has the same form factor as the older miniSD card but the HC card requires HC support built into the host device. MiniSDHC-enabled devices work with miniSD and miniSDHC, but devices without special support for miniSDHC only work with older miniSD cards. Since 2008, miniSD cards are no longer produced.

microSD Secure Digital flash removable flash memory card initially named T-Flash or TF , short for TransFlash . TransFlash and microSD cards are functionally identical allowing either to operate on devices created for others. SanDisk has compiled a microSD when Motorola's chief technology officer and chief technology officer concluded that the current memory card is too large for mobile phones. The card was originally called T-Flash, but shortly before the product launch, T-Mobile sent a stop-and-stop command to SanDisk claiming that T-Mobile had a trademark on T- (whatever), and its name was changed to TransFlash. At CTIA Wireless 2005, SDA announced a small form factor microSD along with SDHC, securing a high-capacity digital format of more than 2 GB with a minimum continuous read and write speed of 17.6 Mbit/s. SanDisk induces SDA to manage microSD standards. SDA approved the final microSD specification on July 13, 2005. Originally, microSD cards were available in 32, 64, and 128 MB capacities.

Motorola E398 is the first mobile phone containing the TransFlash card (later microSD). A few years later, their competitors started using a microSD card.

SD and SDXC

In April 2006, SDA released detailed specifications for non-security related parts of the SD memory card standard and for Secure Digital Input Output (SDIO) cards and standard SD host controllers.

The SDHC format, announced in January 2006, brings enhancements such as 32 GB storage capacity and mandatory support for the FAT32 file system.

In January 2009, SDA announced the SDXC family, which supports cards up to 2 TB and speeds up to 300 MB/s. It features mandatory support for exFAT filesystems.

SDXC announced at the Consumer Electronics Show (CES) 2009 (7-10 January 2009). At the same event, SanDisk and Sony also announced a Memory Stick XC variant that is comparable to the same maximum 2 TB as SDXC, and Panasonic announced plans to produce a 64 GB SDXC card.

On March 6, 2009, Pretec introduced the first SDXC card, 32 GB card with 400 Mbit/s read/write speed. But only in early 2010 compatible host devices came into the market, including Sony Handycam HDR-CX55V camcorders, Canon EOS 550D (also known as Rebel T2i) Digital SLR cameras, Panasonic's USB card readers and integrated JXicron SDXC card readers. The earliest laptops for integrating SDXC card readers rely on USB 2.0 buses, which do not have the bandwidth to support SDXC at full speed.

Also in early 2010, commercial SDXC cards emerged from Toshiba (64Ã,® GB), Panasonic (64Ã, GB and 48Ã, GB), and SanDisk (64Ã, GB). In early 2011, Centon Electronics, Inc. (64Ã, GB and 128Ã, GB) and Lexar (128Ã,® GB) began delivering enhanced SDXC cards in Class 10 Speed. The cards offered from 8 GB to 128 GB were upgraded to Speed ​​Class 16.

In September 2011, SanDisk released a 64 GB microSDXC card. Kingmax released comparable products in 2011.

At the end of 2012, Lexar released the first 256 GB SDXC card, based on NAND 20NM flash technology.

In April 2012, Panasonic introduced the MicroP2 card format for professional video applications. This card is basically a full size SDHC or SDXC UHS-II card, which is rated at UHS Speed ​​Class U1. The adapter allows the MicroP2 card to work in the current P2 card equipment. Panasonic MicroP2 card shipped in March 2013 and is the first UHS-II product in the market; Initial offerings include a 32GB SDHC card and a 64GB SDXC card.

In February 2014, SanDisk introduced the first 128 GB microSDXC card, which was followed by a 200 GB microSDXC card in March 2015. September 2014 saw SanDisk announce the first 512 GB SDXC card.

Samsung announced the 256Ã ¢ microSDXC EVO Plus card, the world's first GB in May 2016. and in September 2016 Western Digital announced that the first 1 TB SDXC prototype prototype will be shown in Photokina.

In August 2017, SanDisk launched a 400 GB microSDXC card. In January 2018, Integral Memory launches a 512 GB microSDXC card.

src: www.totalmedia.com

Market

Secure Digital cards are used in many consumer electronic devices, and have become a widespread means of storing multiple gigabytes of data in small sizes. Devices where users can remove and replace frequent cards, such as digital cameras, camcorders, and video game consoles, tend to use full-size cards. Devices with small size are the most important, like mobile phones, tend to use microSD card.

The microSD card has helped drive the smartphone market by providing greater flexibility and freedom for producers and consumers. Due to its small size, microSD cards are used in many different applications in various markets. Action cameras, such as Hero and GoPRO cameras in drones, often use microSD cards.

The latest versions of major operating systems, including Windows Mobile and Android Marshmallow, allow applications to run from microSD cards creating the possibility for new usage models for SD cards in the mobile computing market.

The SD card is not the most economical solution on a device that requires only a small amount of non-volatile memory, such as a preset station on a small radio. They may also not provide the best option for applications that require storage capacity or higher speeds as provided by other flash card standards such as CompactFlash. This limitation can be overcome by developing memory technology, such as the highest capacity SanDisk Ultra 200GB microSD in the world released in 2015.

Many personal computers of all types, including tablets and phones, use SD cards, either through built-in slots or through an active electronic adapter. Adapter is available for PC, ExpressBus, USB, FireWire, and parallel printer ports. The active adapter also allows SD cards to be used in devices designed for other formats, such as CompactFlash. The FlashPath adapter allows the SD card to be used in a floppy disk drive.

Counterfeit

Commonly found in the market are fake or typo Secure Digital cards that report false or slower-running capacities than those labeled. A software tool exists to check and detect counterfeit products.

Digital camera

SD/MMC card replaces SmartMedia Toshiba as the dominant memory card format used in digital cameras. In 2001, SmartMedia has reached almost 50% of its usage, but in 2005 SD/MMC has reached more than 40% of digital camera market and SmartMedia share dropped in 2007.

At present, all leading digital camera manufacturers use SD in their consumer product line, including Canon, Casio, Fujifilm, Kodak, Leica, Nikon, Olympus, Panasonic, Pentax, Ricoh, Samsung, and Sony. Previously, Olympus and Fujifilm used XD-Picture Cards (xD cards) exclusively, while Sony only used Memory Stick; in early 2010 the third SD is supported.

Some prosumer and professional digital cameras continue to offer CompactFlash (CF), either in the second card slot or as the only storage, since CF supports much higher capacity and is historically cheaper for the same capacity.

Secure Digital memory cards can be used on the Sony XDCAM EX camcorder with adapter and Panasonic P2 card equipment with MicroP2 adapter.

Personal computer

Although many personal computers accommodate SD cards as additional storage devices using built-in slots, or can accommodate SD cards through a USB adapter, SD cards can not be used as primary hard disks through the onboard ATA controllers, since no SD card variants support ATA signaling. The use of a primary hard disk requires a separate SD-controller chip or an SD-to-CompactFlash converter. However, on computers that support bootstrap from the USB interface, the SD card on the USB adapter can be the primary hard disk, provided it contains an operating system that supports USB access after the bootstrap is complete.

Since the end of 2009, newer Apple computers with built-in SD card readers have been able to boot in macOS from SD storage devices, when properly formatted to the Mac OS Extended file format and the default partition table assigned to the GUID Partition Table. (See Other file system below).

Embedded system

In 2008, SDA established Embedded SD, "leverag [ing] the famous SD standard" to enable non-removable SD devices on printed circuit boards. But this standard is not adopted by the market while the MMC standard becomes the de facto standard for embedded systems. SanDisk provides embedded memory components under the iNAND brand.

Most modern microcontrollers have internal SPI logic that can connect to an SD card that operates in its SPI mode, providing non-volatile storage. Even if the microcontroller does not have SPI feature, this feature can be emulated by banging a bit. For example, a home-brew hack combines the General Purpose Input/Output (GPIO) spare pin of the Linksys WRT54G router processor with the MMC support code of the Linux kernel. This technique can achieve throughput of up to 1.6 Mbit/s .

Music distribution

Previously recorded MicroSDs have been used to commercialize music under the brandMusic slot by SanDisk and MQS by Astell & amp; Kern.

src: www.schillers.com

Technical details

Physical size

The SD card specification defines three physical measures. The SD and SDHC families are available in all three sizes, but the SDXC family is not available in miniature, and the SDIO family is not available in micro size. Smaller cards can be used in larger slots through the use of passive adapters.

Standard size

• SD (SDSC), SDHC, SDXC, SDIO
• 32.0ÃÆ'â € "24.0ÃÆ' â €" 2,1mm (1,260ÃÆ'â € "0.945ÃÆ'â €" 0.083 inches) 1,612,8mm ³ (0.09842 in ³ )
• 32.0ÃÆ' â € "24,0ÃÆ'â €" 1,4 mm (1,260ÃÆ' â € "0,945ÃÆ'â €" 0,055 in) 1,075,2 mm ³ (0.06561 in ³ ) (as thin as MMC) for Thin SD (rare)

Mini size

• miniSD, miniSDHC, miniSDIO
• 21,5ÃÆ' â € "20,0ÃÆ'â €" 1,4 mm (0,846ÃÆ'â € 0,787ÃÆ'â € "0,055 in) 602 mm ³ (0,0367 in the soup > 3 )

Micro size

Micro shape factor is the smallest SD card format.

• microSD, microSDHC, microSDXC
• 15,0ÃÆ'â € "11,0ÃÆ'â €" 1,0 mm (0,591ÃÆ'â € "0,433ÃÆ'â €" 0.039 in) 165 mm ³ (0,0101 in ³ )

Transfer mode

The card can support various combinations of bus types and the following transfer modes. SPI bus mode and single-bit SD bus mode are mandatory for all SD families, as described in the next section. Once the host device and SD card negotiate the bus interface mode, the use of numbered pins is the same for all card sizes.

• SPI bus mode: Serial Peripheral Interface Bus is mainly used by embedded microcontrollers. This type of bus only supports 3.3-volt interface. This is the only type of bus that does not require a host license.
• One-bit SD bus mode: Separate command and data channel and ownership transfer format.
• Four-bit SD bus mode: Use an additional pin plus some reassigned pins. This is the same protocol as the one-bit SD bus mode that uses one command and four data paths for faster data transfers. All SD cards support this mode. UHS-I and UHS-II require this type of bus.
• Two line differential SD UHS-II modes: Uses two low voltage differential interfaces to transfer commands and data. The UHS-II card includes this interface in addition to the SD bus mode.

The physical interface consists of 9 pins, except that the miniSD card adds two non-connected pins at the center and the microSD card removes one of the two V sub (Ground) pins.

Note:

1. The direction relative to the card. I = Input, O = Output.
2. PP = Push-Drag logic, OD = Open-Drain logic.
3. S = Power Supply, NC = Unconnected (or logical height).

Interface

The command interface

SD cards and host devices initially communicate via a one-bit sync interface, where the host device provides a clock signal that plugs in single bits into and out of the SD card. The host device thus sends a 48-bit command and receives a response. The card can signal that the response will be delayed, but the host device can cancel the dialog.

By issuing various commands, the host device can:

• Specify the type, memory capacity, and capability of the SD card
• Card orders to use different voltages, different clock speeds, or advanced power interfaces
• Prepare cards to receive blocks to write to flash memory, or read and reply with specified block content.

The command interface is an extension of the MultiMediaCard interface (MMC). The SD card drops support for some commands in the MMC protocol, but adds commands associated with copy protection. By simply using the commands supported by both standards to determine the type of card entered, the host device can accommodate SD card and MMC.

Power interface

All SD card families initially use a 3.3 volt electrical interface. By order, SDHC and SDXC cards can switch to 1.8 V operation.

In power startup or initial card insertion, the host device selects the Serial Peripheral Interface (SPI) bus or a one-bit SD bus with the voltage level present in Pin 1. Afterwards, the host device can issue commands to switch to a four-bit SD bus interface, SD card supports it. For different types of cards, support for a four-bit SD bus is optional or mandatory.

After determining that the SD card supports it, the host device can also instruct the SD card to switch to higher transfer rates. To determine card capability, host devices should not use clock speeds faster than 400 kHz. SD cards other than SDIO (see below) have a clock speed of "Default Speed" of 25 MHz. The host device is not required to use the maximum clock speed that the card supports. It can operate less than the maximum clock speed to save power. Among the commands, the host device can stop the clock completely.

Achieve higher card speed

The SD specification defines a four-bit-wide transfer. (The MMC specification supports this and also defines the eight-bit-width mode: MMC cards with extended bits are not accepted by the market.) Transferring multiple bits on each clock pulse increases the card speed. Advanced SD families have also increased speed by offering faster clock frequencies and dual data rates (described here) in high-speed differential interfaces (UHS-II).

File system

Like other types of flash memory cards, SD cards from each SD family are blockable addressable storage devices, where the host device can read or write fixed-size blocks by specifying the blocking number.

MBR and FAT

Most SD cards are pre-shipped with one or more MBR partitions, where the first or only partitions contain the file system. It lets them operate like a personal computer hard disk. As per SD card specifications, SD cards are formatted with the following MBR and file systems:

• For SDSC cards:
  • Capacity less than 32,680 logical sectors (smaller than 16 MB): FAT12 with partition type 01h and BPB 3.0 or EBPB 4.1
  • Capacity 32.680 to 65.535 logical sectors (between 16 MB and 32 MB): FAT16 with partition type 04h and BPB 3.0 or EBPB 4.1
  • Minimum capacity 65,536 logical sectors (greater than 32 MB): FAT16B with 06h partition type and EBPB 4.1
• For SDHC cards:
  • Capacity less than 16,450,560 logical sectors (smaller than 7.8 GB): FAT32 with partition type 0Bh and EBPB 7.1
  • Minimum capacity 16,450,560 logical sectors (greater than 7.8 GB): FAT32 with partition type 0Ch and EBPB 7.1
• For SDXC card: exFAT with partition type 07h

Most consumer products that take SD cards expect to be partitioned and formatted in this way. Universal support for FAT12, FAT16, FAT16B, and FAT32 allows the use of SDSC and SDHC cards on most host computers with compatible SD readers, to present users with known methods named files in the directory directory hierarchy.

On such SD cards, standard utility programs such as Mac OS X " Disk Utility " or Windows' SCANDISK can be used to repair damaged archiving systems and sometimes recover deleted files. The defragmentation tool for the FAT file system can be used on such cards. Consolidating the generated files can provide marginal improvements at the time it takes to read or write files, but not an improvement comparable to hard drive defragmentation, where storing files in multiple fragments requires physical addition, and is relatively slow, the movement pushing the head. In addition, defragmentation does the writing to the SD card which is calculated against the card's identification period. The writing endurance of physical memory is discussed in an article about flash memory; New technology to increase card storage capacity provides worse writing power.

When reformatting the SD card with a capacity of at least 32 MB (65536 logical sector or more), but not more than 2 GB, FAT16B with 06h partition type and EBPB 4.1 is recommended if the card is for consumer device. (FAT16B is also an option for 4 GB cards, but requires the use of 64 kiB clusters, which are not widely supported.) FAT16B does not support cards above 4 GB at all.

The SDXC specification mandates the use of Microsoft's exFAT file system, which is supported only by some proprietary operating systems.

Other file systems

Because the host views the SD card as a block storage device, the card does not require any MBR partitions or specific file systems. The card can be reformatted to use any file system supported by the operating system. As an example:

• Under Windows, SD cards can be formatted using NTFS and, in newer versions, exFAT.
• Under macOS, SD cards can be partitioned as GUID devices and formatted with the HFS Plus or APFS file system or are still using exFAT.
• Under Unix-like operating systems like Linux or FreeBSD, SD cards can be formatted using the UFS file system, Ext2, Ext3, Ext4, btrfs, HFS Plus, ReiserFS or F2FS. Also on Linux, the HFS Plus file system can be accessed for read/write if the "hfsplus" package is installed, and partitioned and formatted if "hfsprogs" is installed. (The package name is correct under Debian, Ubuntu, etc., but may differ on other Linux distributions.)

Any new version above can format the SD card using the UDF file system.

In addition, as well as live USB flash drives, SD cards can have an operating system installed in them. A computer that can boot from an SD card (either using a USB adapter or inserted into a computer's flash media reader) rather than a hard disk drive can thus recover from a damaged hard disk drive. Such SD cards can be locked-write to maintain system integrity.

SD Standard allows the use of only the Microsoft FAT file system mentioned above and every card produced in the market must be loaded with the relevant standard file system upon delivery to the market. If any application or user reformats the card with a non-standard file system, correct card operation, including interoperability, can not be guaranteed.

Risk of reformatting

Reformatting the SD card with a different file system, or even with the same, can make the card slower, or shorten its life. Some cards use wear leveling, where modified blocks are mapped to different parts of the memory at different times, and some wear-leveling algorithms are designed for typical FAT12, FAT16 or FAT32 access patterns. In addition, previously formatted file systems may use cluster sizes that match the deleted region of physical memory on the card; reformatting can change the size of the cluster and make the writing less efficient.

SD/SDHC/SDXC memory cards have "Protected Area" on the card for standard SD security functions; Standard formatter can delete it, causing problems if security is used. The SD Association provides freely downloadable SD Formatter software to resolve this issue for Windows and Mac OS X. The SD Formatter does not format the "Protected Area", and the Association recommends the use of appropriate software applications or SD compatible devices that provide SD security function to format "Protected Area" on memory card.

Power consumption

SD card power consumption varies based on speed mode, manufacturer, and model.

During transfer it may be in the range of 66-330 mW (20-100 mA at 3.3 V supply voltage). The specifications of the TwinMos technology list are a maximum of 149 mW (45 mA) during transfer. List of Toshiba 264-330 mW (80-100 mA). The standby current is much lower, less than 0.2 mA for a single microSD card 2006. If there is data transfer for significant periods, the battery life can be reduced conspicuously (the smartphone usually has a battery capacity of around 6 Wh (Samsung Galaxy S2, 1650 mAh @ 3.7V)).

Modern UHS-II cards can consume up to 2.88 W, if the host device supports SDR104 or UHS-II bus speed mode. Minimum power consumption in case of UHS-II host is 0.72 W.

src: www.schillers.com

Storage capacity and compatibility

All SD cards allow the host device to determine how much information the card can accommodate, and the specifications of each of the SD families provide the maximum capacity hosted host device that matches the card statement.

By the time the version 2.0 (SDHC) specification was completed in June 2006, vendors have set up 2GB and 4GB SD cards, either as specified in Version 1.01, or by reading Version 1.00 creatively. The resulting card is not working properly on some host devices.

SDSC card above 1 GB

The host device can request an inserted SD card for a 128-bit identification string (Card-Specific Data or CSD). In a standard capacity card (SDSC), 12 bits identify the number of memory groups (ranging from 1 to 4096) and 3 bits identify the number of blocks per cluster (which describes 4, 8, 16, 32, 64, 128, 256, or 512 blocks per cluster). The host device multiplies these numbers (as shown in the following section) by the number of bytes per block to determine the capacity of the card in bytes.

SD version 1.00 is assumed 512 bytes per block. This allows SDSC cards up to 4096 ÃÆ'â € "512 ÃÆ'â €" 512 = 1Ã, GB, with unknown inconsistencies.

Version 1.01 let the SDSC card use the 4-bit field to show 1,024 or 2,048 bytes per block instead. Do it with 2 GB and 4 GB capable cards, such as Transcend 4Ã, GB SD card and 4GB Memorette Memory card.

The initial SDSC host device that considers the 512-byte block does not fully support the insertion of 2 GB or 4 GB cards. In some cases, the host device can read data that happens to be on the first 1 GB card. If the assumptions are made in the driver software, success may depend on the version. Additionally, any host device may not support 4 GB SDSC cards, because the specification allows assuming that 2 GB is the maximum for this card.

Storage capacity calculation

Data-Specific data register (CSD) format changed between version 1 (SDSC) and version 2.0 (which defines SDHC and SDXC).

Version 1

In version 1 of the SD specification, a capacity of up to 2 GB is calculated by combining the CSD fields as follows:

 Capacity = ( C_SIZE  1) ÃÆ'â € "2  ( C_SIZE_MULT  2  READ_BL_LEN )   Where: 0 <=  C_SIZE  <= 4095,  0 <=  C_SIZE_MULT  <= 7,   READ_BL_LEN  is 9 (for 512 bytes/sector) or 10 (for 1024 bytes/sector)  

The final version states (Section 4.3.2) that the SDSC card 2Ã, GB should set READ_BL_LEN (and WRITE_BL_LEN) to indicate 1024 bytes, so the above calculations correctly report card capacity; but that, for consistency, the host device will not prompt (with CMD16) to block the length of more than 512bytes.

Versions 2 and 3

In the definition of the SDHC card in version 2.0, the C_SIZE section of the CSD is 22 bits and this shows the memory size in multiples of 512 KB (C_SIZE_MULT field deleted and READ_BL_LEN is no longer used to calculate capacity). The two previously booked bits now identify the card family: 0 is SDSC; 1 is SDHC or SDXC; 2 and 3 are reserved. Because of this redefinition, older host devices do not correctly identify SDHC or SDXC cards or the correct capacity.

• The SDHC card is limited to reporting capacity of not more than 32 GB.
• The SDXC card is allowed to use all 22 bit C_SIZE fields. The SDHC card that does it (reportedly C_SIZE & gt; 65375 to indicate capacity over 32 GB) will violate the specification. Host devices that rely on C_SIZE rather than specifications to determine maximum card capacity may support such cards, but cards may fail on other SDHC compatible host devices.

Capacity is calculated thus:

 Capacity = ( C_SIZE  1) ÃÆ'â € "524288  where for SDHC 4112 <= C_SIZE <= 65375 (about 2 GB) <= capacity <= 32 GB  for SDXC 65535 <= C_SIZE 32GB <= capacity <= 2TB max.  

Capacities above 4 GB can only be achieved by following version 2.0 or later. In addition, capacity equivalent to 4 GB should also do so to ensure compatibility.

src: www.accessorygenie.com

Openness specification

Like most memory card formats, SD is protected by many patents and trademarks. Royalties for SD card licenses are charged for the manufacture and sale of memory cards and host adapters (US $ 1,000/year plus membership of US $ 1,500/year), but SDIO cards can be made without royalties.

Early versions of the SD specification are only available after approving a non-disclosure agreement (NDA) that prohibits the development of open source drivers. However, the system was eventually reverse engineered, and free software drivers gave access to SD cards that did not use DRM. Since then, SDA has provided a simplified version of the specifications under a less stringent license. Although most open-source drivers are written before this, it has helped solve compatibility issues.

In 2006, SDA released a simplified version of the host controller interface specification (compared to SD card specifications) and later also for physical layer, ASSD extension, SDIO, and SDIO Bluetooth Type-A, under approval disclaimer. Again, most of the information has been found and Linux has free drivers for it. However, creating a chip that fits this specification causes the One Laptop per Child project to claim "the first real Open Source SD implementation, without the need to obtain an SDI license or sign an NDA to create an SD driver or application."

The proprietary nature of complete SD specifications affects embedded systems, laptop computers, and some desktop computers; many desktop computers do not have a card slot, but rather use a USB-based card reader if needed. This card reader presents a standard USB mass storage interface to the memory card, thus separating the operating system from the underlying SD interface details. However, embedded systems (such as portable music players) usually get direct access to the SD card and therefore require complete programming information. Own desktop card reader embedded system; their manufacturers usually pay SDA for complete access to SD specifications. Many notebook computers now include SD card readers that are not USB based; device drivers for this basically get direct access to the SD card, as does the embedded system.

SPI-bus interface mode is the only type that does not require a host license to access the SD card.

src: www.schillers.com

Comparison with other flash memory formats

Overall, SD is less open than CompactFlash or USB flash memory drive. The open standards can be implemented without paying for licenses, royalties, or documentation. (CompactFlash and USB flash drives may require a license fee for the use of the SDA trademarked logo.)

However, SD is much more open than the Memory Stick, where there is no public documentation or documented documented inheritance available. All SD cards can be accessed freely using well-documented SPI buses.

The xD card is just an 18-pin NAND flash chip in a special package and supports standard commands set for raw NAND flash access. Although the raw hardware interface for xD cards is well understood, the layout of its memory content - required for interoperability with xD card readers and digital cameras - is completely undocumented. The consortium licensing the xD card has not released any technical information to the public.

• The table data is compiled from the MMC, SD, and SDIO specifications of the SD Association and the JEDEC website. Data for other card variations is interpolated.

Data recovery

Non-functioning SD cards can be repaired using special equipment, as long as the center contains flash storage, not physically damaged. Controllers can be in this way circumvented.

See also

• Memory card comparison
• Flash memory
• Serial Peripheral Interface Bus (SPI)
• Universal Flash Storage

References

External links

Official

• Official website
• The simplified official free SD specification
• The full specification of the official SD is US $ 1000 per year
• SD format for SD/SDHC/SDXC card (Windows and Mac), SD card

Interfacing

• Connect to SD card , Elm chan Source of the article : Wikipedia