Command
GO_IDLE_STATE
SEND_OP_COND
Command
Busy (still in pwr up)
Response
OCR in R3
Response
CMD2 CID in R2
ALL_SEND_CID
Response
Command
SET_RELATIVE_ADDR
Card status in R1
Response
Command
MMC controller
register
register content
MMC controller
If MMC card has not powered
up fully yet need to re-issue
CMD1 later. If card is ready,
continue will send its OCR.
Identify card by requesting all
cards to send their CID and for
the successful card that sends
it CID, request its RCA.
Continue the CID request and
RCA until all cards are identified.
When there are no more cards to
be identified, there will be no
response and a timeout will be
used to signify the end of the SD
identification process.
Procedures for Common Operations
1285
SPRUH82C – April 2013 – Revised September 2016
Copyright © 2013–2016, Texas Instruments Incorporated
Multimedia Card (MMC)/Secure Digital (SD) Card Controller
Figure 26-11. MMC Card Identification Procedure
26.3.1.2 SD Card Identification Procedure
The SD card identification procedure is:
1. Use the MMC command register (MMCCMD) to issue the GO_IDLE_STATE (CMD0) command to the
MMC cards. Using MMCMD to issue the CMD0 command puts all cards (MMC and SD) in the idle
state and no response from the cards is expected.
2. Use MMCCMD to issue the APP_CMD (CMD55) command (R1 response is expected) to indicate that
the command that follows is an application command.
3. Use MMCCMD to send the SD_SEND_OP_COND (ACMD41) command with the voltage range
supported (R3 response is expected) to SD cards. Using MMCCMD to send the ACMD41 command
allows the host to identify and reject cards that do not match the VDD range that the host supports.
4. Use MMCCMD to send the ALL_SEND_CID (CMD2) command (R2 response is expected) to the MMC
cards. Using MMCCMD to send the CMD2 command notifies all cards to send their unique card
identification (CID) number. There should only be one card that successfully sends its full CID number
to the host. The successful card goes into identification state and does not respond to this command
again.
5. Use MMCMD to issue the SEND_RELATIVE_ADDR (CMD3) command (R1 response is expected) in
order to ask the card to publish a new relative address for future use to address the card in data
transfer mode.
NOTE:
This command is only addressed to the card that successfully sent its CID number in step 4.
This card now goes into standby mode. This card also changes its output drivers from open-
drain to push-pull. It stops replying to the CMD2 command, allowing for the identification of
other cards.