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AT32F435/437
Series Reference Manual
2022.11.11
Page 549
Rev 2.03
Figure 25-4
SDIO sequential read operation
Command
Response
From
host
to card
From
card
to host
Data stop operation
SDIO_D
SDIO_CMD
Response
Data stream
Data from card
to host
Stop command stops data
transfer
Data transfer operation
Command
Figure 25-5
SDIO sequential write operation
Command
Response
From
host
to card
From
card
to host
Data stop operation
SDIO_D
SDIO_CMD
Response
Data stream
Data from host
to card
Stop command stops data
transfer
Data transfer operation
Command
25.3 Functional description
25.3.1 Card functional description
All the communications between the host and the cards are controlled by the card. The host sends two
different types of commands: broadcast command and addressed (point-to-point) command.
Broadcast command: applicable to all cards, some need responses
Addressed command: sent to the addressed card, and responses received from the card
Memory card defines two types of operational modes:
Card identification mode
Data transfer mode
25.3.1.1 Card identification mode
In card identification mode, the host resets all cards, validates the operation voltage range, identifies
cards and sets a relative card address (RCA) for each card on the CMD. All communications in the card
identification mode use the command line (CMD).
Card identification process
The card identification process varies from card to card, and the host sends different commands. There
are SD, SDI/O and MMC cards. It is possible to send a CMD5 command to identify the type of a card. If
the host receives a response, it is a SDI/O card. If no response is received, the host will continue to send
ACMD41 command, if a response is received, it is a SD card, otherwise a MMC card.