GD32W51x User Manual
759
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(D0), 4(D0-D3) or
8(D0-D7).
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 D0-D7 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
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 23-1. SDIO “no response” and “no data” operations
Command
Command
Response
SDIO_CMD
SDIO_D
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
can be configured by the host to use single or multiple data lines.
is the multiple blocks read operation and
is the multiple block write operation. The block write operation uses
a simple busy signal of the write operation duration on the data (D0) line. CE-ATA device has
an optional busy before it is ready to receive the data.