
Figure 21-1: SG-DMA Controller Core with Streaming Peripheral and External Memory
Altera FPGA
SOPC Builde r Syste m
S
Sc atter Gather DMA Controller Core
Nios II
Proc ess or
Rd
SNK
Des criptor
Proce s sor
Blo c k
DDR2
SDRAM
Memory
Controller
M
Rd
M
DMA Write
Block
M
Wr
M
Wr
M
Control
&
Status
Registe rs
System Interco nnect Fa bric
Memory
Desc riptor
Table
S
Avalon-MM Slave Port
SNK
Avalon-ST S ink Port
M
Avalon-MM Master P ort
Stream ing
Com ponent
The figure below shows a different use of the SG-DMA controller core, where the core transfers data
between an internal and external memory. The host processor and memory are connected to a system
bus, typically either a PCI Express or Serial RapidIO
™
.
Figure 21-2: SG-DMA Controller Core with Internal and External Memory
Process or
Bus
Altera FP GA
SOPC Builder Syste m
S
Host Process or
Internal
Memo ry
M M
System Interconnec t Fa bric
S
Rd
M
Des c ripto r
Proces sor
Block
Rd
M
DMA Re ad/
Write
Blo c k
Wr
M
Wr
M
Con trol
&
Stat us
Registe rs
Scatte r Gather DMA Controller Core
Avalon-MM Bridge
M
S
IOB
Main Memo ry
Desc riptor
Table
S
Avalon-MM Slave Por t
M
Avalon-MM Master Port
IOB
IO Breakout
Comparison of SG-DMA Controller Core and DMA Controller Core
The SG-DMA controller core provides a significant performance enhancement over the previously
available DMA controller core, which could only queue one transfer at a time. Using the DMA Controller
core, a CPU had to wait for the transfer to complete before writing a new descriptor to the DMA slave
port. Transfers to non-contiguous memory could not be linked; consequently, the CPU overhead was
substantial for small transfers, degrading overall system performance. In contrast, the SG-DMA controller
core reads a series of descriptors from memory that describe the required transactions and performs all of
the transfers without additional intervention from the CPU.
Resource Usage and Performance
Resource utilization for the core is 600–1400 logic elements, depending upon the width of the datapath,
the parameterization of the core, the device family, and the type of data transfer. The table below provides
21-2
Comparison of SG-DMA Controller Core and DMA Controller Core
UG-01085
2014.24.07
Altera Corporation
Scatter-Gather DMA Controller Core
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