ST STM32F412 Reference Manual page 883

RM0402
The maximum clock frequency for a stream write operation is given by the following
equation fields of the card-specific data register:
•
Maximumspeed = maximum write frequency
• TRANSPEED = maximum data transfer rate
•
writebllen = maximum write data block length
• NSAC = data read access time 2 in CLK cycles
•
TAAC = data read access time 1
•
R2WFACTOR = write speed factor
If the host attempts to use a higher frequency, the card may not be able to process the data
and stop programming, set the OVERRUN error bit in the status register, and while ignoring
all further data transfer, wait (in the receive data state) for a stop command. The write
operation is also aborted if the host tries to write over a write-protected area. In this case,
however, the card sets the WP_VIOLATION bit.
Stream read (MultiMediaCard only)
READ_DAT_UNTIL_STOP (CMD11) controls a stream-oriented data transfer.
This command instructs the card to send its data, starting at a specified address, until the
SDIO card host sends STOP_TRANSMISSION (CMD12). The stop command has an
execution delay due to the serial command transmission and the data transfer stops after
the end bit of the stop command. When the end of the memory range is reached while
sending data and no stop command is sent by the SDIO card host, any subsequent data
sent are considered undefined.
The maximum clock frequency for a stream read operation is given by the following
equation and uses fields of the card specific data register.
•
Maximumspeed = maximum read frequency
•
TRANSPEED = maximum data transfer rate
•
readbllen = maximum read data block length
•
writebllen = maximum write data block length
•
NSAC = data read access time 2 in CLK cycles
•
TAAC = data read access time 1
•
R2WFACTOR = write speed factor
If the host attempts to use a higher frequency, the card is not able to sustain data transfer. If
this happens, the card sets the UNDERRUN error bit in the status register, aborts the
transmission and waits in the data state for a stop command.
Maximumspeed = MIN TRANSPEED
Maximumspeed = MIN TRANSPEED
RM0402 Rev 6
Secure digital input/output interface (SDIO)
8 2 writebllen
( ×
( , ------------------------------------------------------------------------
TAAC
2 readbllen
( 8 ×
( , -----------------------------------------------------------------------
TAAC
) NSAC – ( )
)
× R2WFACTOR
) NSAC – ( )
)
× R2WFACTOR
883/1163
921