Table 220. Command Format; Figure 475. Sdmmc Command Transfer - ST STM32L4x6 Reference Manual

RM0351
• Command format
–
Bit position
47
46
[45:40]
[39:8]
[7:1]
0
–
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.

Figure 475. SDMMC command transfer

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.
Table 220 shows the command format.

Table 220. Command format

Width
1
1
6
32
7
1
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.
DocID024597 Rev 3
SD/SDIO/MMC card host interface (SDMMC)
Table 220.
Figure 475 on page
Value
0 Start bit
1 Transmission bit
- Command index
- Argument
- CRC7
1 End bit
1401.
Description
1401/1693
1450