Parameter
Value
Description
traffic is generated by a DMA engine that is
located in the endpoint application layer logic.
Balanced—configures approximately half the
RX Buffer space to received requests and the
other half of the RX Buffer space to received
completions. Select this option for variations
where the received requests and received
completions are roughly equal.
High—configures most of the RX Buffer space
for received requests and allocates a slightly
larger than minimum amount of space for
received completions. Select this option where
most of the PCIe requests are generated by the
other end of the PCIe link and the local applica‐
tion layer logic only infrequently generates a
small burst of read requests. This option is
recommended for typical root port applications
where most of the PCIe traffic is generated by
DMA engines located in the endpoints.
Maximum—configures the minimum PCIe
specification allowed amount of completion
space, leaving most of the RX Buffer space for
received requests. Select this option when most
of the PCIe requests are generated by the other
end of the PCIe link and the local application
layer logic never or only infrequently generates
single read requests. This option is
recommended for control and status endpoint
applications that don't generate any PCIe
requests of their own and only are the target of
write and read requests from the root complex.
RX Buffer
completion
credits
Header credits, Data credits
Displays the number of completion credits in
the 16 KB RX buffer resulting from the credit
allocation parameter. Each header credit is 16
bytes. Each data credit is 20 bytes.
Table 4-2: RX Buffer Allocation Selections Available by Interface Type
Interface Type
Minimum
Low
Balanced
High
Maximum
Avalon-ST
Available
Available
Available
Available
Available
Avalon-MM
Available
Available
Available
Not Available
Not Available
UG-01145_avmm_dma
2015.11.02
System Settings
4-3
Parameter Settings
Altera Corporation
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