From epark@cam.ac.uk Thu Mar 02 23:11:50 1995
Path: ashpoly!cascade!transat!eunet-fr!teletel!cam!epark
From: epark@cam.ac.uk (Élodie Park)
Newsgroups: comp.dsp
Subject: Fixed-point Q15 arithmetic on Motorola DSP56001 vs IEEE floating point
Message-ID: <1995Mar02.231150.4121@cam.ac.uk>
Date: Thu, 02 Mar 1995 23:11:50 GMT
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Optimizing the Stardust Costas loop demodulator for the Motorola DSP56001 chip.

This leaves over 95% of the DSP56001's 16.5 MIPS available for other audio tasks.
However, when downsampling from 44.1 kHz to 64 Hz, accumulator overflow in the biquad IIR filter can destabilize the loop.

Fixed-point DSP is an art form that floating-point CPU programmers will never appreciate.

-- 
Élodie Park -- University of Cambridge Computer Laboratory
"When every node is whole, the channel opens."

From fgarcia@cam.ac.uk Fri Mar 03 18:01:50 1995
Path: ashpoly!cascade!bigsur!cam!fgarcia
From: fgarcia@cam.ac.uk (Freya García)
Newsgroups: comp.dsp
Subject: Re: Fixed-point Q15 arithmetic on Motorola DSP56001 vs IEEE floating point
Message-ID: <1995Mar03.180150.6008@cam.ac.uk>
Date: Fri, 03 Mar 1995 18:01:50 GMT
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In article <1995Mar02.231150.4121@cam.ac.uk>, epark@cam.ac.uk (Élodie Park) writes:
> Optimizing the Stardust Costas loop demodulator for the Motorola DSP56001 chip.

Ran your code on my NeXTstation Turbo. It locked onto the carrier within 1.2 seconds of vinyl lead-in.

-- 
=== Freya García ===
Dept of Electrical Engineering, University of Cambridge Computer Laboratory
"The hatch is open. Is anyone listening?"