By PURPLELEC | 27 September 2023 | 0 Comments
What is sd card internal structure
In addition to retaining the 7-pin MMC card, the SD card interface also adds 2 extra pins on both sides as data lines.
In the SD card 3.0 specification, the theoretical maximum capacity of the SD card can reach 2TB, and the theoretical maximum read and write speed can reach 104MB/s (in the latest 4.10 specification, the theoretical maximum read and write speed has been increased to 312MB/s).
The SD card is mainly divided into four parts: external pins, internal registers, interface controller and internal storage media.
(1) The main pins and functions are described as follows:
CLK: Clock signal. The controller or SD card transmits a command bit or data bit in each clock cycle. In the default speed mode of the SD bus, the frequency can vary between 0 and 25MHz. The bus manager of the SD card can be affected by the The freedom to generate frequencies from 0 to 25MHz under any restrictions, with clock frequencies up to 208M in UHS-I speed mode.
CMD: Command and response multiplexing pin. The command is sent by the controller to the SD card, either from the controller to a single SD card or to all cards on the SD bus; the response is the command sent by the memory card to the controller. Response, the response can come from a single card or all cards.
DAT0～3: Data line, data can be transmitted from the card to the controller or from the controller to the card.
(2) The registers and functions are described as follows:
OCR (Operating Conditions Register) register: The 32-bit operating conditions register mainly stores the VDD voltage range. The SD card operating voltage range is 2~3.6V.
CID (Card IDentification Register) register: Card identification code register, 16 bytes in length, stores the SD card unique identification number, which cannot be modified after programming by the card manufacturer.
CSD (Card-Specific Data Register) register: Card characteristic data register, which contains the necessary configuration information when accessing the card data.
SCR (SD Card Configuration Register) register: SD card configuration register (SCR) provides some special features of the SD card in this card. The length is 64 bits. The content of this register is set by the manufacturer in the production factory.
RCA (Relative Card Address) register: The card relative address register is a 16-bit writable address register. The controller can select the SD card with the corresponding address through the address.
DSR (Driver Stage Register) register: Driver stage register, which is an optional register and is used to configure the driver output of the card.
(3) Interface controller
Mainly used to control and manage the internal storage core, control and set it by receiving commands sent by users, respond according to the commands, and then perform operations such as reading and writing the corresponding data.
(4) Internal storage media
Flash block of data memory storage.
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