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AT32F435/437
Series Reference Manual
2022.11.11
Page 547
Rev 2.03
25
SDIO interface
25.1 SDIO introduction
The SD/SDIO MMC card host interface (SDIO) provides an interface between the AHB peripheral bus
and MultiMediaCards (MMC), SD memory cards and SDIO cards.
SD memory card and SDI/O card system specifications are available through the SD card association
website www.sdcard.org.
The MultiMediaCard system specifications published by the MMCA technical committee are available
through the MultiMediaCard association website www.mmca.org.
25.2 SDIO main features
Full compatibility with SD memory card specifications version 2.0
Full compatibility with SDI/O card specification version 2.0 and support 1-bit and 4-bit databus
modes.
Full compatibility with MultiMedia card specification version 4.2 and support 1-bit, 4-bit and 8-bit
databus modes.
Full compatibility with previous versions of MultiMedia card specifications
DMA transfer
Data transfer up to 50 MHz in 8-bit bus mode
Interrupt requests
Note: The SDIO is not compatible with SPI communication mode. It supports only one
SD/SDIO/MMC 4.2 card at any one time.
Communication on the bus is based on command and data transfers.
―
Command: A command is a token that starts an operation. Commands are sent from the host
either to a single card (addressed command) or to all connected cards (broadcast command).
Commands are transferred serially on the CMD line.
―
Response: A response is a token that is sent from a card to the host as an answer to a
previously received command. Responses are transferred serially on the CMD line.
―
Data: Data can be transferred from the card to the host or vice versa. Data is transferred via
the SDIO_D data line.
The basic operation on the MMC card/SD/SDI I/O bus is the command/response structure. These types
of bus operation transfer their information through the command or bus mechanism. In addition, some
operations have a data token.
Data transfers to/from SD/SDIO memory cards are done in data blocks. Data blocks are always followed
by CRC bit, defining single and multiple block operations. Data transfers to/from MMC are done in data
blocks or streams, as shown in Figure below.