Altera Cyclone V Device Handbook page 748

11-70
Alternative Boot Operation for MMC4.3 Cards
• The DMA descriptor is closed.
• The ces bit in the idsts register is set to 1, indicating Boot Data Start timeout.
• The ri bit of the idsts register is not set.
b. If a Boot Data Start interrupt is received, the boot data is being received from the card device. When
the DMA engine is not in internal DMA controller mode, the software driver can then initiate a data
read from the controller based on the rxdr interrupt bit in the rintsts register.
In internal DMA controller mode, the DMA engine starts transferring the data from the FIFO buffer
to the system memory as soon as the level specified in the rx_wmark field of the fifoth register
is reached.
c. The software driver must terminate the boot process by instructing the controller to send the SD/SDIO
GO_IDLE_STATE (CMD0) command:
• Reset the cmdarg register to 0.
• Set the start_cmd bit in the cmd register to 1, and all other bits to 0.
d. At the end of a successful boot data transfer from the card, the following interrupts are generated:
• The cmd bit and dto bit in the rintsts register
• The ri bit in the idsts register, in internal DMA controller mode only
e. In internal DMA controller mode:
• If the software driver creates more descriptors than required by the received boot data, the extra
descriptors are not closed by the controller.
• If the software driver creates fewer descriptors than required by the received boot data, the controller
generates a Descriptor Unavailable interrupt and does not transfer any further data to system
memory.
The alternative boot operation for eMMC card devices is complete.
Related Information
• Clock Setup
Refer to this section for information on how to set the card device frequency.
• Internal DMA Controller Transmission Sequences
Refer to this section for information about the Internal DMA Controller Transmission Sequences.
• Internal DMA Controller Reception Sequences
Refer to this section for information about the Internal DMA Controller Reception Sequences.
Alternative Boot Operation for MMC4.3 Cards
Removable MMC4.3 Boot Mode Support
Removable MMC4.3 cards differ with respect to eMMC in that the controller is not aware whether these
cards support the boot mode of operation. Thus, the controller must:
1. Discover these cards as it would discover MMC4.0/4.1/4.2 cards for the first time
2. Know the card characteristics
3. Decide whether to perform a boot operation or not
Altera Corporation
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SD/MMC Controller
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2013.12.30
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