CLK: clock signal. The controller or SD card sends a command bit or data bit every clock cycle. In the default speed mode of SD bus, the frequency can vary from 0 to 25 MHz. The bus manager of SD card can generate frequencies from 0 to 25 MHz freely without any restrictions. In UHS-I speed mode, the clock frequency can reach up to 208M m.
CMD: command and response multiplexing pin. Commands are sent from the controller to the SD card, which can be sent from the controller to a single SD card or to all cards on the SD bus. The response is the response of the memory card to the command sent by the controller, which can come from a single card or all cards. ? [ 1]?
Dat 0 ~ 3: data line, data can be transmitted from the card to the controller or from the controller to the card.
Extended data:
Reasons for canceling TF card of mobile phone:
1, mobile phone internal arachis duranensis.
No matter how small the TF card is, including the shell and card slot, it is much larger than a single memory chip. In order to make the mobile phone slimmer and increase its functions, it is necessary to reduce the functions that occupy space, such as memory cards. In fact, the sim card has changed from big to small, also in order to reduce the occupation.
2. There is a gap between speed and stability.
No matter how good the memory card is, there is a speed limit. Compared with dedicated chips, there are bottlenecks in speed and stability. In particular, memory cards produced by some small factories may have a greater impact. Because of a memory card, the mobile phone program is unstable and runs smoothly, and the mobile phone doesn't want to carry this pot.
3. User demand decision.
In the past, when the memory of mobile phones was 8G and 16G, the requirements for memory cards were higher. Now mobile phone storage has started at 64G, so for most people, this capacity is enough, and there is absolutely no need to add additional storage.
Baidu encyclopedia -microsd card