Main pins and functions of SD card

CLK: clock signal. The controller transmits one command bit or data bit in each clock cycle. Under the default speed mode of the SD bus, the frequency can vary from 0 to 25MHz. The bus manager of the SD card can freely generate a frequency of 0 to 25MHz without any restrictions. Under the uhs-i speed mode, the clock frequency can be up to 208m.

CMD: Command and response multiplexing pin. The command is sent from the controller to the SD card. It can be from the controller to a single SD card or to all cards on the SD bus; The response is a command response sent by the memory card to the controller. The response can be 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.

The pin definition of SD card is different from that of micro SD (TF) card.

SD card: 1-data3,2-cmd, 3-vss, 4-vdd, 5-clk, 6-vss, 7-data0,8-data1,9-data2

TF Card (SD mode): 1-data2,2-data3,3-cmd, 4-vdd, 5-clk, 6-vss, 7-data0,8-data1

TF Card (SPI mode): 1-rsv, 2-cs, 3-di, 4-vdd, 5-sclk, 6-vss, 7-do, 8-rsv