DocID018909 Rev 11
RM0090
Secure digital input/output interface (SDIO)
1067
Figure 331. SDIO 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
. CE-ATA commands are an
extension of MMC commands V4.2, and so have the same format.
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.
–
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 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.
Table 150. 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
SDIO_CK
SDIO_CMD
Command
Response
Command
State
Idle
Send
Wait
Receive
Idle
Send
Hi-Z
Controller drives
Hi-Z
Card drives
Hi-Z
Controller drives
ai14707
at least 8 SDIO_CK cycles