SD cards are compact and portable, they are used for storing data such as photos, videos, games, or audio files.They have a capacity of up to 2TB and a speed of 900MB/s.">

SD cards - Everything you need to know !

SD, mini SD, micro SD :  the dimensions.
SD, mini SD, micro SD : the dimensions.

SD cards :

Portable Storage : SD cards offer a compact and portable solution for data storage, allowing users to easily carry files, photos, videos, and other types of data between different devices.


Memory expansion : SD cards allow the storage capacity of electronic devices such as smartphones, tablets, digital cameras, camcorders, game consoles, etc., to be expanded, providing more space to store apps, media, and other files.

Data backup : SD cards can be used as a backup medium to back up important data, providing a convenient and portable backup solution to protect data from loss or corruption.

Media Capture : SD cards are widely used to capture photos, videos, and audio recordings in digital cameras, camcorders, smartphones, etc. They offer a reliable and fast storage solution for recording high-resolution media.

File Transfer : SD cards can be used to transfer files between different devices, including computers, cameras, smartphones, tablets, etc., providing a convenient method for sharing data between multiple devices.

Critical Data Storage : SD cards can be used to store critical data such as business files, confidential documents, creative projects, and more, providing a secure and portable storage solution for both business users and creatives.

Operation

Flash Memory :
Most SD cards use flash memory chips to store data. Flash memory is a type of solid-state memory that retains data even when it is not powered by electricity. This technology is non-volatile, which means that the data remains intact even when the power is turned off.

  • Organization of memory :
    The flash memory in an SD card is organized into blocks and pages. Data is written and read in blocks. A block contains a number of pages, which are the smallest units of writing or reading data. The memory organization is managed by a controller built into the SD card.

  • SD Controller :
    Each SD card is equipped with a built-in controller that handles the operations of writing, reading, and erasing data on the card. The controller also handles wear management operations to ensure optimal SD card life.

  • Communication interface :
    SD cards use a standardized communication interface to interact with host devices, such as cameras or smartphones. This interface can be SD (Secure Digital), SDHC (Secure Digital High Capacity) or SDXC (Secure Digital eXtended Capacity), depending on the capacity and speed of the card.

  • Communication protocol :
    The communication protocol used by SD cards is based on the SPI (Serial Peripheral Interface) bus or the SDIO (Secure Digital Input Output) bus, depending on the type of card and its application. These protocols allow host devices to transfer data to and from the SD card reliably and efficiently.

  • Data protection :
    SD cards are often equipped with data protection features, such as physical switches to write lock data on the card. This prevents accidental or unauthorized changes to the data stored on the card.


The connections between the SD card and the drive.
The connections between the SD card and the drive.

Connections

An SD card's connections are the pins or electrical contacts that establish a connection between the SD card and the reader, allowing communication and data transfer between the card and the host device (e.g., a computer, camera, smartphone, etc.).
Here are the connections found on an SD card reader :

  • Data pins :
    Data pins are used to transfer data between the SD card and the drive. There are usually multiple data pins to allow for fast and efficient data transfers. The number of data pins may vary depending on the type of SD card (SD, SDHC, SDXC) and transfer speed.

  • Power Spindles :
    The power pins provide the power supply needed for the SD card to operate. They allow the board to receive the electrical energy needed to operate and perform read and write operations.

  • Control pins :
    The control pins are used to send commands and control signals to the SD card. They allow the reader to communicate with the SD card and give it instructions to perform various operations, such as reading, writing, erasing, etc.

  • Insertion detection pins :
    Some SD cards and card readers are equipped with insert detection pins that automatically detect when the SD card is inserted or removed from the reader. This allows the host device to react accordingly, such as by mounting or unmounting the SD card as a storage device.

  • Other pins :
    In addition to the pins mentioned above, there may be other pins on an SD card reader for specific functions or advanced features, such as power management, data protection, etc.


Evolution of storage capacities and transfer speeds .
Evolution of storage capacities and transfer speeds .

Evolution

SD cards have undergone several evolutions over the years to meet the growing needs in terms of storage capacity, transfer speed, and advanced features.
Here are some of the latest developments in SD cards :
SDHC (Secure Digital High Capacity) SDHC cards are an evolution of standard SD cards, offering a storage capacity of more than 2 GB up to 2TB. They use an exFAT file system to handle the large storage capacity.
SDXC (Secure Digital eXtended Capacity) SDXC cards represent another major evolution in terms of storage capacity. They can store up to 2 TB (terabytes) of data, although the capacities available on the market are generally less than that. SDXC cards also use the exFAT file system.
UHS-I (Ultra High Speed) The UHS-I standard allows for faster data transfer speeds compared to standard SDHC and SDXC cards. UHS-I cards use a dual-line data interface to improve performance, achieving read speeds of up to 104 MB/s and write speeds of up to 50 MB/s.
UHS-II (Ultra High Speed II) UHS-II SD cards represent a further evolution in terms of transfer speed. They use a two-line data interface and add a second row of pins to allow for even faster transfer speeds. UHS-II cards can reach read speeds of up to 312MB/s.
UHS-III (Ultra High Speed III) UHS-III is the latest evolution in transfer speed for SD cards. It uses a two-line data interface with even faster transfer rates than UHS-II. UHS-III cards are capable of reading speeds of up to 624MB/s.
SD Express The SD Express standard is a recent evolution that combines the functionality of SD cards with PCIe (PCI Express) and NVMe (Non-Volatile Memory Express) storage technology. This allows for extremely high data transfer speeds, potentially exceeding 985 MB/s.


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