
SD/SDIO/MMC card host interface (SDMMC)
RM0351
1526/1830
DocID024597 Rev 5
Figure 498. SDMMC command transfer
•
Command format
–
Command: a command is a token that starts an operation. Command are sent
from the host either to a single card (addressed command) or to all connected
cards (broadcast command are available for MMC V3.31 or previous). Commands
are transferred serially on the CMD line. All commands have a fixed length of 48
bits. The general format for a command token for MultiMediaCards, SD-Memory
cards and SDIO-Cards is shown in
.
The command path operates in a half-duplex mode, so that commands and
responses can either be sent or received. If the CPSM is not in the Send state, the
SDMMC_CMD output is in the Hi-Z state, as shown in
.
Data on SDMMC_CMD are synchronous with the rising edge of SDMMC_CK.
shows the command format.
–
Response: a response is a token that is sent from an addressed card (or
synchronously from all connected cards for MMC V3.31 or previous), to the host
as an answer to a previously received command. Responses are transferred
serially on the CMD line.
The SDMMC supports two response types. Both use CRC error checking:
•
48 bit short response
•
136 bit long response
Note:
If the response does not contain a CRC (CMD1 response), the device driver must ignore the
CRC failed status.
Table 265. Command format
Bit position
Width
Value
Description
47
1
0
Start bit
46
1
1
Transmission bit
[45:40]
6
-
Command index
[39:8]
32
-
Argument
[7:1]
7
-
CRC7
0
1
1
End bit
DLE
6'00&B&.
6'00&B&0'
&RPPDQG
5HVSRQVH
&RPPDQG
6WDWH
,GOH
6HQG
:DLW
5HFHLYH
,GOH
6HQG
+L=
&RQWUROOHUGULYHV
+L=
&DUGGULYHV
+L=
&RQWUROOHUGULYHV
DWOHDVW6'00&B&.
F\FOHV