Internal Structure of The SD card substrate

Besides featuring a 7-pin SD card substrate interface with card power supply, card detection, and reset, the SD card interface also incorporates two additional pins on both sides as data pins. The SD card, this specific SD card will have a storage capacity between 0 and the theoretical maximum size of 2TB, and read/write speeds of up to 104MB / s. The SD card is mainly divided into four parts: I/O interface and peripherals including external pins, special registers or interface controller, and internal storage units.

CLK: Clock signal: The controller more commonly known as the SD card is capable of transmitting one command bit or data bit in every single clock cycle.

CMD: The SSH1 protocol has a command and response multiplexing pin. This is initiated by the controller to a specific card or to all cards that are on the SD bus; this is a response to the control initiated by the memory card with the controller. Response, the response may be performed by one card, or by all of them.

DAT: Data line, data can transit in the SD card substrate or from the card to the controller or from the controller to the card.

The registers and functions are:

OCR (Operating Conditions Register) register: There are also thirty-two-bit operating conditions registers that primarily hold the vdd voltage range.

CID (Card Identification Register) register: This is a 16-byte long register that has the identification code for the SD card and this code cannot be changed by any party after the card has been programmed by the card manufacturer.

CSD (Card-Specific Data Register) register: Information register, which is needed, when accessing the card characteristics, as is shown in the previous subsection.

SCR (SD Card Configuration Register) register: The SCR in this card sets some special features of the SD card as follows: It is of 64-bit length. The kind of content contained in this register is developed by the manufacturer at the manufacturing center.

RCA (Relative Card Address) register: The card relative address register is one of the writable address registers which is 16-bit in size. Through the address for the chosen address, the controller can choose the SD card that belongs to that particular address.

DSR (Driver Stage Register) register: this is another optional register out of the card and it is used to set the driver output of the card.

Interface controller

This SD card substrate serves fundamentally in regulating and governing the internal storage core; it signals for setting and receives various commands from users and then performs operations such as reading and writing the correct data based on the signals it receives.

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