UM10503
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© NXP B.V. 2012. All rights reserved.
User manual
Rev. 1.3 — 6 July 2012
424 of 1269
NXP Semiconductors
UM10503
Chapter 20: LPC43xx SD/MMC interface
20.6.12 Command Register (CMD)
Table 308. Command Register (CMD, address 0x4000 402C) bit description
Bit
Symbol
Value
Description
Reset
value
5:0
CMD_INDEX
Command index
0
6
RESPONSE_EXPECT
Response expect
0
0
No response expected from card
1
Response expected from card
7
RESPONSE_ LENGTH
Response length
0
0
Short response expected from card
1
Long response expected from card
8
CHECK_RESPONSE_
CRC
Check response crc. Some of command responses do not return valid
CRC bits. Software should disable CRC checks for those commands
in order to disable CRC checking by controller.
0
0
Do not check response CRC
1
Check response CRC
9
DATA_EXPECTED
Data expected
0
0
No data transfer expected (read/write)
1
Data transfer expected (read/write)
10
READ_WRITE
read/write. Don't care if no data expected from card.
0
0
Read from card
1
Write to card
11
TRANSFER_MODE
Transfer mode. Don't care if no data expected.
0
0
Block data transfer command
1
Stream data transfer command
12
SEND_AUTO_STOP
Send auto stop. When set, the SD/MMC interface sends stop
command to SD_MMC_CEATA cards at end of data transfer. Refer to
to determine:
- when send_auto_stop bit should be set, since some data transfers
do not need explicit stop commands
- open-ended transfers that software should explicitly send to stop
command
Additionally, when resume is sent to resume - suspended memory
access of SD-Combo card - bit should be set correctly if suspended
data transfer needs send_auto_stop. Don't care if no data expected
from card.
0
0
No stop command sent at end of data transfer
1
Send stop command at end of data transfer
13
WAIT_PRVDATA_
COMPLETE
Wait prvdata complete. The wait_prvdata_complete = 0 option
typically used to query status of card during data transfer or to stop
current data transfer; card_number should be same as in previous
command.
0
0
Send command at once, even if previous data transfer has not
completed.
1
Wait for previous data transfer completion before sending command.