Table 183. Command Format; Figure 375. Sdio Command Transfer - ST STM32F423 Reference Manual

Secure digital input/output interface (SDIO)
• Command format
–
Bit position
47
46
[45:40]
[39:8]
[7:1]
0
–
The SDIO 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.
1034/1324

Figure 375. SDIO 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
SDIO_CMD output is in the Hi-Z state, as shown in
Data on SDIO_CMD are synchronous with the rising edge of SDIO_CK.
shows the command format.

Table 183. 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.
Table 183.
Value
0
1
-
-
-
1
RM0430 Rev 8
Figure 375 on page 1034.
Table 183
Description
Start bit
Transmission bit
Command index
Argument
CRC7
End bit
RM0430