SD Card Input/Output Protocol Controller

SDIO protocol is evolved and upgraded from the SD card protocol. In many places, the SD card read-write protocol is retained. At the same time, the SDIO protocol adds cmd52 and cmd53 commands to the SD card protocol. Because of this, an important difference between SDIO and SD card specifications is the addition of low-speed standard. The target application of low-speed card is to support low-speed I / O capability with minimum hardware expenditure. MMC is the abbreviation of multimedia card. In essence, it is a memory card specification for solid-state nonvolatile storage , which defines aspects such as card shape, size, capacity, electrical signal, communication protocol between host and so on. Since the MMC specification was released in 1997, different specifications such as MMC, SD, microSD,SDIO and EMMC have been evolved based on different considerations (physical size, voltage range, number of pins, maximum capacity, data bit width, clock frequency, security characteristics, whether SPI mode is supported, whether DDR mode is supported, etc.). Although the flowers are charming, their essence remains the same after all, which is why the Linux kernel calls them MMC.

• Compliance with Embedded MultiMediaCard System Specification Version 4.51. Card support for three different databus modes: 1-bit (default), 4-bit and 8-bit
• Full compatibility with previous versions of MultiMediaCards (backward compatibility)
• Full compliance with SD memory card specifications version 4.2 ( SPI mode and UHS-II mode not supported)
• Full compliance with SDIO card specification version 4.0 Card support for two different databus modes: 1-bit (default) and 4-bit (SPI mode and UHS-II mode not supported)
• Supports SDIO slave mode (only IO mode)