Sd3.0 protocol explanation 1

Preface:

I recently studied SD/mmccard drivers, and the SD/MMC drivers I have studied should all know that the SD/MMC protocol is an essential part, unless you do not want to study the SD/MMC driver thoroughly, you can only study the files in the driver/MMC/host directory. Speaking of the SD/MMC protocol, the sd3.0 protocol is only available in English versions. To really understand the protocol, poor English can be difficult, however, there are few Chinese documents related to the sd3.0 protocol on the Internet. The old man is angry and wants to write his understanding of the sd3.0 protocol, so the interpretation of this series of sd3.0 protocols will be coming soon .....

System features:

Card capacity:

1. Standard capacity card (SDSC): The maximum capacity is 2 GB

2. High Capacity card (sdhc): The capacity is 2 ~ 32 GB card

3. Extended capacity card (sdxc): The capacity is 32 GB ~ 2 TB card

Q: What is the purpose? Where can I use it?

A: The SD card is generally used as an external expansion capacity, so the cards used by different users are definitely different. to distinguish different cards, during the initialization and Identification Card Process of sd3.0, the user will determine which card the user inserts is in SDSC/sdhc/sdxc, for example, when the 38bit CCS in R3 is 0 B, indicates that the inserted card is an SDSC card, while the CCS = 1b indicates that the inserted card is an sdhc or sdxc card. Different cards have minor differences in cammand and response. Let's talk about them later.

Voltage range:

Operating voltage range: 2.7 ~ 3.6 V

Q: What is the purpose of voltage range?

A: The work of the card is not single-edged. It interacts with the CPU controller (host), so the host also has its own supported voltage, the card end also has its own supported voltage, which may be different. For example, host supports 1.8 ~ 3.8 V, while card supports 2.7 ~ 3.6 V, and the protocol is used to take the intersection and help the host and card coordinate the voltage supported by everyone.

Card attributes:

The card can be designed as a read-only card and a readable/writable card.

Four-Line bus speed mode:

What do you mean by reading it? Isn't the English level worse than the old one? It's really too bad to install a Kingsoft word overlord ~~ Here we will explain the two abbreviations. SDR means single data rate (single data sampling, in other words, either rising edge sampling or falling edge sampling ), DDR means double data rate (bilateral data sampling, in other words, bilateral Edge Sampling ).

Note that these bus speed modes are only supported in the four-line mode. If it is in the one-line mode, it may be different, not all hosts support all modes. For example, not all CPUs support sdr104 mode. This requires strong Io Input and Output capabilities, even if you can run 1.8 GHz clock speed, the IO on the SD card may not necessarily support 208 MHz. This depends on the CPU spec.

Well, I have written so much in this article. Note that the old man doesn't simply translate the sd3.0 English protocol, but only parse the English language. This is not an understanding of the Protocol, here is the protocol!