DocID024597 Rev 3 1401/1693
RM0351 SD/SDIO/MMC card host interface (SDMMC)
1450
Figure 475. 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 Table 220.
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 Figure 475 on page 1401.
Data on SDMMC_CMD are synchronous with the rising edge of SDMMC_CK.
Table 220 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 220. 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
DLE
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6'00&B&0'
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&RPPDQG
6WDWH ,GOH 6HQG :DLW 5HFHLYH ,GOH 6HQG
+L= &RQWUROOHUGULYHV +L= &DUGGULYHV +L= &RQWUROOHUGULYHV
DWOHDVW6'00&B&.
F\FOHV
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