The Digital signal processor reference article from the English Wikipedia on 24-Apr-2004 (provided by Fixed Reference: snapshots of Wikipedia from wikipedia.org)

Digital signal processor

A Digital Signal Processor (DSP) is a specialized microprocessor designed specifically for digital signal processing, generally in real-time. DSPs can also be used to perform general-purpose computation, but they are not optimised for this function.

Rather than general computations, DSPs usually have an instruction set (ISA) optimised for the task of rapid signal processing, often using the following techniques:

• Multiply-accumulate (MAC) operations (good for all kinds of matrix operations).
• Deep pipelining.
• The ability to act as a Direct Memory Access device for the host environment.
• Saturation arithmetic, in which operations that produce overflows will accumulate at the maximum (or minimum) values that the register can hold rather than wrapping around (maximum+1 doesn't equal minimum as in many general-purpose CPUs, instead it stays at maximum).
• Separate program and data memories (Harvard architecture).
• Most DSPs are fixed-point, because in real world signal processing, extra precision is often not required, and there is a large speed benifit; however, floating point DSPs are common for scientific and other applications where precision is required.
• Specialized instructions for modulo addressing in ring buffers and bit-reversed addressing mode for FFT cross-referencing.

Generally, DSPs are dedicated integrated circuits, however DSP functionality can also be realised using Field Programmable Gate Array chips. Present-day general-purpose microprocessors also have ideas and influences from digital signal processors, such as the MMX extensions in the Intel IA-32 architecture.

History

In the 1978, Intel released 2920 as "analog signal processor". It had on-chip ADC/DAC with internal signal processor. But it didn't have hardware multiplier. The 2920 was not successful in the market. In 1979, AMI released S2811. S2811 was designed as microprocessor peripheral. Its register had to been initialized by host, and program had to be downloaded from host. The S2811 was not successful in the market, neither.

Presented in 1980 was the first stand-alone complete DSP, the NEC µPD7710 and AT&T DSP1 in the ISSCC '80. Both processor was inspired by the research about PSTN telecomunication. In this year, NEC started the production of µPD7710, that was world first production of complted DSP.

The first DSP produced by Texas Instruments, the TMS32010 presented in 1983, proved to be an even bigger success.

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