
Secure digital input/output interface (SDIO)
RM0008
Doc ID 13902 Rev 12
interface using a protocol that utilizes the existing MMC access primitives. The interface
electrical and signaling definition is as defined in the MMC reference.
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.
22.2
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 206. SDIO “no response” and “no data” operations
Figure 207. SDIO (multiple) block read operation
Operation (no response)
Operation (no data)
SDIO_CMD
SDIO_D
From host to card(s)
From host to card
From card to host
Response
Command
Command
ai14734
ai14735
Command
Response
Data block crc
Data block crc
Data block crc
Block read operation
Multiple block read operation
Data stop operation
From host to card
From card to host
data from card to host
Stop command
stops data transfer
Command
Response
SDIO_CMD
SDIO_D