Tashkent university of information technologies subject of operating systems

SD card structure
In addition to the 7 pins of the MMC card, the SD card interface is also added to the two edges as a data line.
In the SD card 3.0 specification, the maximum capacity of the SD card can reach 2TB. The maximum read and write speed of the theory can reach 104 MB / s (in the last 4.10 specification, the theoretical maximum read and write speed increased to 312 MB / s).


SD card structure
The SD card is basically divided into four parts: external pins, internal registers, interface controllers, and internal memory devices.
Pin
The main pins and functions of the SD card are:
CLK: The clock signal, controller, or SD card transmits a command bit or data bit each clock cycle. The frequency can vary from 0 to 25 MHz in the standard speed mode of the SD bus, and the bus manager of the SD card generates the frequency freely from 0 to 25 MHz. In UHS-I speed mode, the clock frequency can be up to 208 m.
CMD: Reading the command and response, the command is sent by the controller to the SD card, which can be from the controller to a single SD card or to all the cards on the SD bus. The answer is a command sent by the memory card. The answer can come from a single card or from all cards.
Dat0 ~ 3: The data cable can also be transferred from the data manager to the card.
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The register and its functions are described below:
OCR - (operating conditions register): The 32-bit operating conditions register mainly stores the VDD voltage range, and the SD card operating voltage range is 2 ~ 3.6V.
CID - (CARD Identification Register) register: The card identification code register is 16 bytes long and the unique identification number of the SD card is stored. This number cannot be changed once the card manufacturer has been programmed.
CSD - (Card-Specific Data Register): The Carter Data Register contains the configuration information required to access card data.
SCR - (SD CARD Configuration Register): The SD card configuration register (SCR) provides some special features with a 64-bit SD card, and the contents of this register are set by the manufacturer.
RCA - (Relative Card Address) register: The card's relative address register is a 16-bit writeable address register. The controller can select the SD card that matches the location by location.