GD32F10x User Manual
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Each message is represented by one of the following tokens:
Command
: a command is a token which starts an operation. A command is sent from the
host to a card. A command is transferred serially on the CMD line.
Response
: a response is a token which is sent from the card to the host as an answer to a
previously received command. A response is 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 data lines. The number of data lines used for the data transfer can be 1(DAT0), 4(DAT0-
DAT3) or 8(DAT0-DAT7).
The structure of commands, responses and data blocks is described in
. One data transfer is a bus operation.
There are different types of operations. Addressed operations always contain a command
and a response token. In addition, some operations have a data token; the others transfer
their information directly within the command or response structure. In this case no data token
is present in an operation. The bits on the DAT0-DAT7 and CMD lines are transferred
synchronous to the host clock.
Two types of data transfer commands are defined:
Stream commands: These commands initiate a continuous data stream; they are
terminated only when a stop command follows on the CMD line. This mode reduces the
command overhead to an absolute minimum (only MMC supports).
Block-oriented commands: These commands send a data block successfully by CRC
bits. Both read and write operations allow either single or multiple block transmission. A
multiple block transmission is terminated when a stop command follows on the CMD line
similarly to the sequential read.
The basic transaction on the bus is the command/response transaction (refer t
19-1. SDIO “no response” and “no data” operations
). This type of bus transaction
transfers their information directly within the command or response structure. In addition,
some operations have a data token. Data transfers to/from the Card/Device are done in
blocks.
Figure 19-1. SDIO “no response” and “no data” operations
Command
Command
Response
SDIO_CMD
SDIO_DAT
Operation (no response)
Operation (no data)
Host to Device
Host to Device
Device to Host
Note that the Multiple Block operation mode is faster than Single Block operation. A multiple
block transmission is terminated when a stop command follows on the CMD line. Data transfer
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