GD32F403xx User Manual
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the card may not be able to process the data and will stop programming, and while ignoring
all further data transfer, wait (in the Receive-data-State) for a stop command. As the host
sends CMD12, the card will respond with the TXURE bit set and return to Transfer state
Stream read
There is a
stream oriented data transfer controlled by READ_DAT_UNTIL_STOP (CMD11).
This command instructs the card to send its data, starting at a specified address, until the
host sends a STOP_TRANSMISSION command (CMD12). The stop command has an
execution delay due to the serial command transmission. The data transf er stops af ter the
end bit of the stop command.
If the host provides an out of range address as an argument to CMD11, the card will reject
the command, remain in Transfer state and respond with the ADDRESS_OUT_OF_RANGE
bit set.
Note that the stream read command works only on a 1 bit bus configuration (on DAT0). If
CMD11 is issued in other bus configurations, it is regarded as an illegal command.
If the end of the memory range is reached while sending data, and no stop command has
been sent yet by the host, the contents of the further transferred payload is undefined. As the
host sends CMD12 the card will respond with the ADDRESS_OUT_OF_RANGE bit set and
return to Tran state.
In order to sustain data transfer in stream mode of the card, the time it takes to transmit the
data (defined by the bus clock rate) must be less than the time it takes to read it out of the
main memory field (defined by the card in the CSD register). Therefore, the maximum clock
frequency for stream read operation is given by the following formula:
max read frequence = min(TRAN_SPEED,
8∗2
READ_BL_LEN
−100∗NSAC
TAAC∗R2W_FACTOR
)
(20-3)
TRAN_SPEED
: Max bus clock frequency.
READ_BL_LEN
: Max read data block length.
NSAC
: Data read access-time 2 in CLK cycles.
TAAC
: Data read access-time 1.
R2W_FACTOR
: Write speed factor.
All the parameters are defined in CSD register. If the host attempts to use a higher frequency,
the card may not be able to process the data and will stop programming, and while ignoring
all further data transfer, wait (in the Receive-data-State) for a stop command. As the host
sends CMD12, the card will respond with the RXORE bit set and return to Transfer state
20.6.6.
Erase
The erasable unit of the MMC/SD memory is the “Erase Group”; Erase group is measured in