Altera cyclone V Technical Reference page 1018

14-72
Card Read Threshold Programming Examples
Table 14-37: Legal Values of dw_dma_multiple_transaction_size and rx_wmark for Block Size = 512
Block Size
512
512
512
512
512
512
512
Card Read Threshold Programming Examples
This section shows examples of how to program the card read threshold.
• Choose a block size that is a multiple of 4 (the number of bytes per FIFO location), and less than 4096
(1024 FIFO locations). For example, a block size of 3072 bytes is legal, because 3072 / 4 = 768 FIFO
locations.
• For DMA mode, choose the size so that block size is a multiple of the size. For example size = 128,
where block size%size = 0.
• Set the
• Because block size > ½ FifoDepth, set the
cardrdthreshold
Figure 14-16: FIFO Buffer content when Card Read Threshold is set to 768
Read Data
to Host
Altera Corporation
dw_dma_multiple_transaction_size
1
4
8
16
32
64
128
†
†
field = size – 1. For example, the
rx_wmark
field = 3072 bytes.
256 FIFO Locations
Unfilled During One
Block Read
One Block of Data Filled 768 FIFO Locations
0
3
7
15
31
63
127
field = 128 – 1 = 127.
rx_wmark
field to the block size. For example, the
cardrdthreshold
†
Block Size = cardrdthreshold = 768
FIFO Depth = 1,024
rx_wmark
†
†
†
SIZE = 128
FIFO Locations
rx_wmark = 127
FIFO Locations
SD/MMC Controller
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cv_5v4
2016.10.28
†
Data Read
from Card