FPGAs for DSP Hardware
- the advantages and disadvantages of using FPGAs rather than DSP processors
in the DSP hardware.
When designing the hardware system for a DSP application it
is necessary to carefully consider the approach that will be taken. One of the
fundamental decisions involves whether to use a standard DSP processor, or
whether to use an FPGA in the DSP hardware. Each has its own advantages and they
need to be carefully balanced at the earliest stages of the design.
DSP processor
A DSP processor is a specialised processor that is designed
specifically for operating complex mathematically orientated intensive
calculations very swiftly. As processing needs to be undertaken almost in real
time, the speed of the processor is one of the main limiting performance
criteria for the performance of the system For example very steep filters need
more processing than those that are not so steep, etc..
While DSP processors, despite their sophistication in terms
of processing have limitations, they also have advantages. One of these is in
their cost. They may still be expensive by some standards, but they are
nevertheless cheaper than their counterparts, the FPGA.
FPGAs for DSP
The other approach that many adopt is to use an FPGA as the
core of the DSP hardware. These devices can be programmed and there are many set
cores that can be used to provide the routines that are required. For example if
a filter is required, then it is possible to tailor circuitry within the FPGA to
undertake this. Similarly other functions can be programmed in on top of the
basic processor. In this way the FPGA is able to be programmed to provide a
highly efficient and tailored solution.
The main disadvantage of the FPGA is its cost. FPGAs are more
costly that DSP processors and therefore performance has to be weighed against
cost.
Summary
FPGAs and DSP processors provide two very different
approaches to the design of DSP hardware systems. Each have their own
advantages. There are many high sampling rate applications that an FPGA does
easily, while the DSP could not. Equally, there are many complex software
problems that the FPGA cannot address.
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