24-09-2012, 01:40 PM
FPGA BASED EMBED SYSTEM
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INTRODUCTION
Embedding a processor inside an FPGA has many advantages.
Unique user-designed peripherals being easily attached. A variety of
memory controllers enhance the FPGA embedded processor systems
interface capabilities.
FPGA embedded processors use general-purpose FPGA logic to
construct internal memory, processor busses, internal peripherals, and
external peripheral controllers.
As more pieces (busses, memory, memory controllers, peripherals, and
peripheral controllers) are added to the embedded processor system,
the system becomes increasingly more powerful and useful.
FPGA Embedded Processors
The Field Programmable Gate Array (FPGA) is a general-purpose
device lled with digital logic building blocks.
The two market leaders in the FPGA industry, Altera and Xilinx, are
the focus of this study. Many
The most primitive FPGA building block is called either a Logic Cell
(LC) by Xilinx or a Logic Element (LE) by Altera.
In either case, this building block consists of a look-up table (LUT)
for logical functions and a
ip-
op for storage.
In addition to the LC/LE block, FPGAs also contain memory, clock
management, input/output (I/O), and multiplication blocks. For the
purposes of this study, LC/LE consumption is used in determining
system cost.
Customization
The designer of an FPGA embedded processor system has complete
exibility to select any combination of peripherals and controllers.
In fact, the designer can invent new, unique peripherals that can be
connected directly to the processors bus.
For example, a designer would not easily nd an o-the-shelf
processor with ten UARTs. However, in an FPGA, this conguration
is very easily accomplished.
Component and cost reduction
With the versatility of the FPGA, previous systems that required
multiple components can be replaced with a single FPGA. Certainly
this is the case when an auxiliary I/O chip or a co-processor is
required next to an o-the-shelf processor.
By reducing the component count in a design, a company can reduce
board size and inventory management, both of which will save design
time and cost.
Hardware acceleration
Perhaps the most compelling reason to choose an FPGA embedded
processor is the ability to make tradeos between hardware and
software to maximize eciency and performance.
If an algorithm is identied as a software bottleneck, a custom
co-processing engine can be designed in the FPGA specically for that
algorithm.
With modern FPGA hardware design tools, transitioning software
bottlenecks from software to hardware is much easier since the
software C code can be readily adapted into hardware with only minor
changes to the C code.1
Disadvantages
Unlike an o-the-shelf processor, the hardware platform for the FPGA
embedded processor must be designed.
Because of the integration of the hardware and software platform
design, the design tools are more complex.
Since FPGA embedded processor software design is relatively new
compared to software design for standard processors, the software
design tools are likewise relatively immature, although workable.
If a standard, o-the-shelf processor can do the job, that processor
will be less expensive in a head-to-head comparison with the FPGA
capable of an equivalent processor design.