Digital Signal Processors (DSP's)


A Digital Signal Processor, or DSP, is a semiconductor device used for processing signals digitally.  A signal, in this context, traditionally refers to an analog signal (such as analog voltage) that has been converted into a digital one so that it can be processed mathematically.  Nowadays, however, almost every piece of information has been digitized, so a digital signal may be any stream of digital data - digital audio/video data, betting odds, or even the weight of clothes in a washing machine.  Analysis of such digital signals for a variety of purposes can be easily accomplished by a DSP.


Signal processing encompasses a large variety of actions performed on signals - filtering, encoding/decoding, compression/decompression, amplification, modulation, level detection, pattern matching, mathematical/logical operations, and much more. These processes are performed on a signal for a number of reasons: to enhance it; reduce its component noise; make its transmission and reception more effective, efficient, and faster; transform it; make it interact with other signals in special ways; facilitate its use in digital analysis, monitoring, or control; etc. A DSP has built-in capabilities to perform these signal processing functions easily.     


A DSP is very similar to a microprocessor.  In fact, it is regarded by many as a special microprocessor created particularly to process signals.  Both a microprocessor and a DSP can execute instructions, accept input digital data, perform operations on them, and output digital data. The fundamental difference between a DSP and a microprocessor is what their built-in processing capabilities were designed for. 


A DSP is a highly-specialized device that's equipped with a multitude of mathematical functions specifically intended for processing a digital signal, whereas a microprocessor is designed to be a general-purpose device.  A microprocessor would be able to handle many different applications, such as word processing, spreadsheets, databases, and, well, even digital signal processing.  However, it can not be as good as a DSP when it comes to serious DSP applications.


Current trends in technology seem to indicate the possibility though that the distinction between a DSP and a microprocessor will soon be gone. Microprocessors are becoming more and more sophisticated that some of them are now equipped with true DSP capabilities.  It will just be a matter of time before high-end microprocessors will have the capability to perform high-end signal processing, or any high-end task for that matter.


A DSP is also very similar to a microprocessor as far as architecture is concerned, i.e., it has many parts that are also seen in a microprocessor, such as data and address buses, an Arithmetic-Logic Unit (ALU), a program control unit, assorted flags and registers, etc. It also has its own native instruction set, which defines what it can be programmed to do. Programming DSP's is no longer complicated too, with the existence of various development kits in the market that support DSP software development using high-level programming languages such as C.


Many DSP applications deal with real-world analog signals (such as sound, light, analog voltage, analog current, temperature, pressure). Since a DSP can only process digital signals, there is a need to convert analog signals first into digital data before they can be processed by a DSP.  After processing, there is again a need for the DSP to convert these digital data back into the original real-world analog signal format. In such applications, the DSP must be supported by an analog-to-digital converter (ADC) and a digital-to-analog converter (DAC), which will perform the required analog-digital and digital-analog conversions, respectively.


Applications where DSP's are commonly used include:  1) digital sound and image processing; 2) digital communications; 3) consumer electronics (e.g., mobile phones, faxes, computer peripherals such as modems and sound cards, and digital entertainment systems such as DVD players and digital TV); 4) medical electronics; and 5) industrial and automation electronics.


There are currently four major companies that produce DSP's, namely, Texas Instruments, Analog Devices, Motorola, and Lucent Technologies.  Examples of commercially available DSP's include:


- Analog Devices' ADSP-21xx: 10 to 50 MIPS 16-bit fixed-point DSP's; 40-bit accumulator; 24-bit instructions;

- Analog Devices' ADSP-2106x ("SHARC"): 40 MIPS, 32-bit floating point DSP's;

- Lucent Technologies' DSP32xx: 32-bit floating-point with 40-bit accumulator and 16/24-bit fixed point DSP's;

- Motorola's DSP568xx: 20 MIPS 16-bit fixed-point DSP's;

- Motorola's DSP96002: IEEE format floating-point DSP with two complete 32-bit data and address buses;
- Texas Instruments'
TMS320C1x: Low cost fixed-point DSP's with 16-bit data, 32-bit registers;

- Texas Instruments' TMS320C8x: Multiple 50 MHz 32-bit fixed-point processors combined with a RISC supervisory processor in a single multi-chip module.


See also:   DAC'sADC's Microprocessors;  What is a Semiconductor?




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