What is the difference between SD and SDIO

 

Often, the embedded engineers do get confused with the SD interface and SDIO interface. The main reason for this is that the interface looks similar as shown below.

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As it can be seen from the above interface diagram, SD card interface is to interface memory devices like the SD cards. SDIO is to communicate to a device with SDIO interface. Basically, SDIO is a communication interface. Remember that SD interface can also be used for MMC card.

When we talk about the SDIO interface, the intention is to provide high speed interface with low power consumption. As we talked about the Wi-Fi/BT chip set in the above interface diagram, we see such scenarios in the commercial applications often and so it is a common interface.

As we talk about the common physical interface between the SD and SDIO, the maximum frequency of operation is 208 MHz in either case.

SD Association defines 2 different cards as below:

• SD Card
• Storage
• Storage + I/O
• I/O (like the SDIO)

If a SDIO card is inserted into the non-SDIO card slot, then shall be no physical damage as both are electrically compatible. When we say electrical compatibility, we are talking from the electrical levels perspective.