Initialization † - Altera cyclone V Technical Reference

cv_5v4
2016.10.28
Software Issues a
If the software issues a
state machines are reset; the FIFO is not cleared. The DMA sends all remaining bytes to the host. In
addition to a card-reset, if a FIFO reset is also issued, then:
• Any pending DMA transfer on the bus completes correctly
• DMA data read is ignored
• Write data is unknown (x)
Additionally, if dma_reset is also issued, any pending DMA transfer is abruptly terminated. When the
DW-DMA/Non-DW-DMA is used, the DMA controller channel should also be reset and reprogrammed.
If any of the previous data commands do not properly terminate, then the software should issue the FIFO
reset in order to remove any residual data, if any, in the FIFO. After asserting the FIFO reset, you should
wait until this bit is cleared.
Data-Transfer Requirement Between the FIFO and Host
One data-transfer requirement between the FIFO and host is that the number of transfers should be a
multiple of the FIFO data width (
write only 15 bytes to an
program the DMA to do 16-byte transfers, if external DMA mode is enabled. The software can still
program the Byte Count register to only 15, at which point only 15 bytes will be transferred to the card.
Similarly, when 15 bytes are read from a card, the host should still read all 16 bytes from the FIFO.
It is recommended that you not change the FIFO threshold register in the middle of data transfers when
DW-DMA/Non-DW-DMA mode is chosen.
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Initialization
After the power and clock to the controller are stable, the controller active-low reset is asserted. The reset
sequence initializes the registers, FIFO buffer pointers, DMA interface controls, and state machines in the
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controller.
SD/MMC Controller
Send Feedback
Command
Controller_Reset
controller_reset
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F_DATA_WIDTH
SD_MMC_CEATA
Software Issues a Controller_Reset Command
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command by setting control register bit[0] to 1, all the CIU
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). For example, if
card ( ), the host should write 16 bytes to the FIFO or
BYTCNT
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= 32 and you want to
F_DATA_WIDTH
14-41
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Altera Corporation