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Gaussian Noise Generator Code for Texas TMS320C54x/C55x & C2xx/C5x DSPs

This routine generates random noise samples with a Gaussian distribution. The code is based on a pseudo-random sequencer which repeats every ~2x10⁹ samples. The sequencer output is converted into samples with Probability Density Function (PDF) and Cumulative Distribution Function (CDF) Gaussian distributions. The crest factor, i.e. the peak signal sample relative to the Root-Mean-Square (RMS) sample value, is 6.15. Thus for a set# RMS value of 4096 decimal, the peak signal obtainable is ~±25,000 (#by assembler equate). The software is in the form of two callable subroutines, one for start-up initialisation and one for generation of each sample. Successive calls of the main routine generate successive noise samples that are uncorrelated. The code is re-entrant so multiple noise generators in one DSP can readily be implemented.

Performance: (values measured over complete pseudo random cycle)

• RMS error: 0.0004dB

• Correlation: =-66dB (adjacent 4 samples)

• PDF error: =0.002

• CDF error: =2%

Full measured performance results are available.

DSP Load:

• MIPs: 0.33 @ 8kHz s.r.

• Data memory (words): 3(scratch) + 2(permanent)

• Program Memory (words): 0.13k

Availability: NOW - sale is under licence. Integration support can be provided.