Introduction to DSP - DSP processors: characteristics

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