STM32F101xx, STM32F102xx, STM32F103xx, STM32F105xx and ...

RM0008
Secure digital input/output interface (SDIO)
The MultiMediaCard/SD bus connects cards to the controller.
The current version of the SDIO supports only one SD/SDIO/MMC4.2 card at any one time
and a stack of MMC4.1 or previous.
20.2 SDIO bus topology
Communication over the bus is based on command and data transfers.
The basic transaction on the MultiMediaCard/SD/SD I/O bus is the command/response
transaction. These types of bus transaction transfer their information directly within the
command or response structure. In addition, some operations have a data token.
Data transfers to/from SD/SDIO memory cards are done in data blocks. Data transfers
to/from MMC are done data blocks or streams. Data transfers to/from the CE-ATA Devices
are done in data blocks.
Figure 177. SDIO “no response” and “no data” operations
From host to card(s) From host to card From card to host
SDIO_CMD
Command
Command
Response
SDIO_D
Operation (no response)
Operation (no data)
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Figure 178. SDIO (multiple) block read operation
From host to card
From card to host
data from card to host
Stop command
stops data transfer
SDIO_CMD
Command
Response
Command
Response
SDIO_D
Data block crc Data block crc Data block crc
Block read operation
Multiple block read operation
Data stop operation
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Doc ID 13902 Rev 9 457/995