Altera cyclone V Technical Reference page 990

14-44
Card Type is Either SDIO COMBO or Still in Initialization
a. Send an SD/SDIO IO_SEND_OP_COND (CMD5) command with argument 0 to the card.
b. Read
voltage that the card supports.
c. Send the IO_SEND_OP_COND command, with the desired voltage window in the arguments. This
command sets the voltage window and makes the card exit the initialization state.
d. Check bit 27 in
• If bit 27 is 0, the SDIO card is IO ONLY. In this case, proceed to
• If bit 27 is 1, the card type is SDIO COMBO. Continue with the following steps.
3. Go to Card Type is Either SDIO COMBO or Still in Initialization
4. Go to Determine if Card is a CE-ATA 1.1, CE-ATA 1.0, or MMC Device
5. At this point, the software has determined the card type as SD/SDHC, SDIO or SDIO-COMBO. Now it
must enumerate the card stack according to the type that has been discovered.
6. Set the card clock source frequency to the frequency of identification clock rate, 400 KHz. Use one of
the following discovery command sequences:
• For an SD card or an SDIO memory section, send the following SD/SDIO command sequence:
• GO_IDLE_STATE
• SEND_IF_COND
• SD_SEND_OP_COND (ACMD41)
• ALL_SEND_CID (CMD2)
• SEND_RELATIVE_ADDR (CMD3)
• For an SDIO card, send the following command sequence:
• IO_SEND_OP_COND
• If the function count is valid, send the SEND_RELATIVE_ADDR command.
• For an MMC, send the following command sequence:
• GO_IDLE_STATE
• SEND_OP_COND (CMD1)
• ALL_SEND_CID
• SEND_RELATIVE_ADDR
7. You can change the card clock frequency after discovery by writing a value to the
divides down the
The following list shows typical clock frequencies for various types of cards:
• SD memory card, 25 MHz
• MMC card device, 12.5 MHz
• Full speed SDIO, 25 MHz
• Low speed SDIO, 400 kHz
Related Information
SD Association
To learn more about how SD technology works, visit the SD Association website (www.sdcard.org).
Card Type is Either SDIO COMBO or Still in Initialization
Only continue with this step if the SDIO card type is COMBO or there is no response received from the
previous IO_SEND_OP_COND command. Otherwise, skip to
Type section.
1. Send the SD/SDIO SEND_IF_COND (CMD8) command with the following arguments:
Altera Corporation
on the controller. The response to the IO_SEND_OP_COND command gives the
resp0
:
resp0
clock.
sdmmc_clk
†
†
†
†
step 5.
on page 14-44.
on page 14-45.
clkdiv
step 5 of the Identifying the Connected Card
cv_5v4
2016.10.28
register that
SD/MMC Controller
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