Although there are many DSP processors, they are mostly designed with the same few basic operations in mind: so they share the same set of basic characteristics. These characteristics fall into three categories:
- specialised high speed arithmetic
- data transfer to and from the real world
- multiple access memory architectures
Typical DSP operations require a few specific operations:
The diagram shows an FIR filter. This illustrates the basic DSP operations:
- additions and multiplications
- delays
- array handling
Each of these operations has its own special set of requirements:
additions and multiplications require us to:
- fetch two operands
- perform the addition or multiplication (usually both)
- store the result or hold it for a repetition
delays require us to:
- hold a value for later use
array handling requires us
to:
- fetch values from consecutive memory locations
- copy data from memory to memory
To suit these fundamental operations DSP processors often have:
- parallel multiply and add
- multiple memory accesses (to fetch two operands and store the result)
- lots of registers to hold data temporarily
- efficient address generation for array handling
- special features such as delays or circular addressing
