DocID018909 Rev 11
RM0090
Secure digital input/output interface (SDIO)
1067
select a different card), which will place the card in the Disconnect state and release the
SDIO_D line(s) without interrupting the write operation. When selecting the card again, it will
reactivate busy indication by pulling SDIO_D to low if programming is still in progress and
the write buffer is unavailable.
31.4.6 Block
read
In Block read mode the basic unit of data transfer is a block whose maximum size is defined
in the CSD (READ_BL_LEN). If READ_BL_PARTIAL is set, smaller blocks whose start and
end addresses are entirely contained within one physical block (as defined by
READ_BL_LEN) may also be transmitted. A CRC is appended to the end of each block,
ensuring data transfer integrity. CMD17 (
READ_SINGLE_BLOCK
) initiates a block read and
after completing the transfer, the card returns to the Transfer state.
CMD18 (
READ_MULTIPLE_BLOCK
) starts a transfer of several consecutive blocks.
The host can abort reading at any time, within a multiple block operation, regardless of its
type. Transaction abort is done by sending the stop transmission command.
If the card detects an error (for example, out of range, address misalignment or internal
error) during a multiple block read operation (both types) it stops the data transmission and
remains in the data state. The host must than abort the operation by sending the stop
transmission command. The read error is reported in the response to the stop transmission
command.
If the host sends a stop transmission command after the card transmits the last block of a
multiple block operation with a predefined number of blocks, it is responded to as an illegal
command, since the card is no longer in the data state. If the host uses partial blocks whose
accumulated length is not block-aligned and block misalignment is not allowed, the card
detects a block misalignment error condition at the beginning of the first misaligned block
(ADDRESS_ERROR error bit is set in the status register).
31.4.7
Stream access, stream write and stream read
(MultiMediaCard only)
In stream mode, data is transferred in bytes and no CRC is appended at the end of each
block.
Stream write (MultiMediaCard only)
WRITE_DAT_UNTIL_STOP
(CMD20) starts the data transfer from the SDIO card host to the
card, beginning at the specified address and continuing until the SDIO card host issues a
stop command. When partial blocks are allowed (CSD parameter WRITE_BL_PARTIAL is
set), the data stream can start and stop at any address within the card address space,
otherwise it can only start and stop at block boundaries. Because the amount of data to be
transferred is not determined in advance, a CRC cannot be used. When the end of the
memory range is reached while sending data and no stop command is sent by the SD card
host, any additional transferred data are discarded.
