Digital Signal Processors

Digital Signal Processors

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

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

A DSP is very similar toa microprocessor.  Infact, it is regarded by many as a special microprocessor createdparticularly to process signals.  Both a microprocessor and a DSPcan execute instructions, accept input digital data, perform operations onthem, and output digital data. The fundamental difference between a DSP and amicroprocessor is what their built-in processing capabilities weredesigned for. 

A DSP is a highly-specializeddevice that's equipped with a multitude of mathematical functions specificallyintended for processing a digital signal, whereas a microprocessor is designedto be a general-purpose device.  A microprocessor would be able to handlemany different applications, such as word processing, spreadsheets, databases,and, well, even digital signal processing.  However, it can not be as goodas a DSP when it comes to serious DSP applications.   

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

A DSP is also verysimilar to a microprocessor as far as architecture is concerned, i.e., it hasmany parts that are also seen in a microprocessor, such as data and addressbuses, an Arithmetic-Logic Unit (ALU), a program control unit, assortedflags and registers, etc. It also has its own native instruction set, whichdefines what it can be programmed to do. Programming DSP's is no longercomplicated too, with the existence of various development kits in the marketthat support DSP software development using high-level programming languagessuch as C.

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

Applications whereDSP'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 entertainmentsystems such as DVD players and digital TV); 4) medical electronics; and 5)industrial and automation electronics.

There are currentlyfour major companies that produce DSP's, namely, Texas Instruments, AnalogDevices, Motorola, and Lucent Technologies.  Examples of commerciallyavailable DSP's include:

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

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

- LucentTechnologies' DSP32xx: 32-bit floating-point with 40-bit accumulator and16/24-bit fixed point DSP's;

- Motorola's DSP568xx: 20MIPS 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;

- TexasInstruments' TMS320C8x: Multiple 50 MHz 32-bit fixed-point processorscombined with a RISC supervisory processor in a single multi-chip module.

Reference: http://www.siliconfareast.com