Altera Cyclone V Device Handbook page 701

cv_54011
2013.12.30
• Stream-read for MMC with byte count greater than zero The controller generates an internal STOP
command and loads it into the command path so that the end bit of the STOP command is sent when
the last byte of data is read from the card and no extra data byte is received. If the byte count is less than
six (48 bits), a few extra data bytes are received from the card before the end bit of the STOP command
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is sent.
• Stream-write for MMC with byte count greater than zero The controller generates an internal STOP
command and loads it into the command path so that the end bit of the STOP command is sent when
the last byte of data is transmitted on the card bus and no extra data byte is transmitted. If the byte count
is less than six (48 bits), the data path transmits the data last to meet these condition.
• Multiple-block read memory for SD card with byte count greater than zero If the block size is less than
four (single-bit data bus), 16 (4-bit data bus), or 32 (8-bit data bus), the AUTO_STOP command is loaded
in the command path after all the bytes are read. Otherwise, the STOP command is loaded in the command
path so that the end bit of the STOP command is sent after the last data block is received.
• Multiple-block write memory for SD card with byte count greater than zero If the block size is less than
three (single-bit data bus), 12 (4-bit data bus), or 24 (8-bit data bus), the AUTO_STOP command is
loaded in the command path after all data blocks are transmitted. Otherwise, the STOP command is
loaded in the command path so that the end bit of the STOP command is sent after the end bit of the
CRC status is received.
• Precaution for host software during auto-stop When an AUTO_STOP command is issued, the host
software must not issue a new command to the controller until the AUTO_STOP command is sent by
the controller and the data transfer is complete. If the host issues a new command during a data transfer
with the AUTO_STOP command in progress, an AUTO_STOP command might be sent after the new
command is sent and its response is received. This can delay sending the STOP command, which transfers
extra data bytes. For a stream write, extra data bytes are erroneous data that can corrupt the card data.
If the host wants to terminate the data transfer before the data transfer is complete, it can issue an SD/SDIO
STOP or STOP_TRANSMISSION (CMD12) command, in which case the controller does not generate
an AUTO_STOP command.
Auto-Stop Generation for MMC Cards
Table 11-10: Auto-Stop Generation for MMC Cards
Transfer Type
Stream read
Stream read
Stream write
Stream write
Single-block read
Single-block write
Multiple-block read
SD/MMC Controller
Send Feedback
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Byte Count send_auto_stop bit set
0 No
>0 Yes
0 No
>0 Yes
>0 No
>0 No
0 No
Auto-Stop Generation for MMC Cards
Comments
Open-ended stream
Auto-stop after all bytes transfer
Open-ended stream
Auto-stop after all bytes transfer
Byte count = 0 is illegal
Byte count = 0 is illegal
Open-ended multiple block
11-23
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