SD/MMC/sdio concept Differentiation

SD/MMC/sdio concept Differentiation

 

SD (securedigital) and MMC (multimediacard)

SD is a standard for flash memory card, which is a common SD memory card. MMC is an earlier standard for memory cards and has been replaced by SD. On Wikipedia, we have a detailed description of SD/MMC specifications: [http://zh.wikipedia.org/wiki/secure_digital.pdf.

 

Sdio (securedigital I/O)

Sdio is a technology that we are currently concerned about. sdio's old name is "interface" of SD. However, there may be some samples for this explanation. More specifically, SD is the standard for memory cards, but now we can also use it to plug in some peripheral interfaces. This technology is sdio.

Therefore, sdio itself is a simple technology that connects external peripherals through the sd I/O connector and transmits data with these peripherals through the I/O data slots on SD, in addition, SD Association members also launched a complete sdio stack driver, making development and application of sdio peripherals (called sdio cards) quite popular.

Many mobile phones and handheld devices now support sdio functions (SD standard was originally set for mobile devices), and many sdio peripherals have been developed, it makes the external peripheral of the mobile phone easier and more flexible in Development (no built-in peripheral is required ). Currently, common sdio peripherals (sdio cards) include:

· Wi-fi card (Wireless Network Card)

· CMOS sensor card (CAMERA module)

· GPS card

· GSM/GPRS modem card

· Bluetooth card

· Radio/TV card (fun)

The Application of sdio will be one of the most important interface technologies of embedded systems in the future, and will replace the current gpio-type SPI interface.

Transmission Mode of SD/sdio

There are three SD transmission modes:

· SPI mode (required)

· 1-Bit mode

· 4-Bit mode

Sdio also supports the above three transmission modes. According to SD standard, all SD (memory card) and sdio (peripheral) must support SPI mode, so SPI mode is "required 」. In addition, early MMC cards (transmitted using SPI) can also be connected to SD slots and read using SPI mode or 1-Bit mode.

 

Secure Digital I/ocard, pin out

 

SD mmcmode

SD can also read the MMC memory. Although the MMC standard mentions that the MMC memory does not necessarily support SPI mode (but must support 1-Bit mode ), however, the MMC cards available on the market all support SPI mode. Therefore, we can set SD to the SPI mode transmission mode to read the MMC memory card.

Sd mmc mode is a transmission mode used to read the MMC card. However, although sd mmc mode also uses SPI mode, its physical features are still different:

· The maximum transmission rate of mmc spi mode is 20 Mbit/s;

· SD's maximum SPI mode transmission rate is 25 Mbit/s.

To avoid confusion, the SPI/MMC mode and SPI/SD mode are also used to make a clear distinction.

Reference: https://www.sdcard.org/developers/overview/capacity/

Http://www.interfacebus.com/Secure_Digital_IO_Card_Pinout.html