RM0008 Secure digital input/output interface (SDIO)
Doc ID 13902 Rev 12 551/1096
Figure 216. 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 Table 1 3 7 . 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 Figure 216 on page 551. Data
on SDIO_CMD are synchronous with the rising edge of SDIO_CK. Tabl e 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 137. 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
011End 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
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