Discovering Removable MMC4.3 Boot Mode Support
For removable MMC4.3 cards, the software driver must perform the following steps:
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1. Discover the card as described in
Enumerated Card Stack
.
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2. Read the MMC card device’s EXT_CSD registers and examine the following fields:
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• BOOT_PARTITION_ENABLE
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• BOOT_SIZE_MULT
†
• BOOT_INFO
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For more information, refer to "Access to Boot Partition” in JEDEC Standard No. JESD84-A43,
available on the JEDEC website.
†
Note:
3. If the host processor needs to perform a boot operation at the next power-up cycle, it can manipulate the
contents of the EXT_CSD registers in the MMC card device, by using a SWITCH_FUNC command.
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4. After this step, the software driver must power down the card by writing to the
pwren
register.
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5. From here on, use the same steps as in
Alternative Boot Operation for eMMC Card Devices
.
†
Ignore the EBE if it is generated during an abort scenario.
If a boot acknowledge error occurs, the boot acknowledge received interrupt times out.
†
Note:
In internal DMA controller mode, the application needs to depend on the descriptor close interrupt
instead of the data done interrupt.
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Related Information
•
on page 11-31
Refer to this section for more information on discovering removable MMC cards.
•
For more information, refer to "Access to Boot Partition” in JEDEC Standard No. JESD84-A43, available
on the JEDEC website.
•
Alternative Boot Operation for eMMC Card Devices
on page 11-67
Refer to this section for information about alternative boot operation steps.
Voltage Switches
This section describes the general steps to switch voltage level.
The SD/MMC cards support various operating voltages, for example 1.8V and 3.3V. If you have a card which
is at 1.8V and you eject it and replace it with another card, which is 3.3V, then voltage switching is required.
In order to have the right voltage level to power the card, separate devices on the board are required: voltage
translation transceiver and power regulator/supply. When the software is aware that voltage switching is
needed, it should control the power regulator to supply another voltage level to the card (i.e. switching
between 1.8V and 3.3V).
However, for the HPS (or Altera device), the I/O pins are connected to the SD/MMC card running at 3.3V.
If your card runs at 1.8V, the voltage-translation transceiver is needed for voltage translation between the
HPS and the SD/MMC card.
Altera Corporation
SD/MMC Controller
11-71
Discovering Removable MMC4.3 Boot Mode Support
cv_54011
2013.12.30