From ysantos@earthlink.net Fri Oct 13 05:11:57 1995
Path: ashpoly!cascade!mxgate!coyoacan!earthlink!ysantos
From: ysantos@earthlink.net (Yuki Santos)
Newsgroups: comp.dsp
Subject: [FLAME] Fixed-point Q15 arithmetic on Motorola DSP56001 vs IEEE floating point
Message-ID: <1995Oct13.051157.9443@earthlink.net>
Date: Fri, 13 Oct 1995 05:11:57 GMT
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Optimizing the Stardust Costas loop demodulator for the Motorola DSP56001 chip.

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

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

-- 
Yuki Santos
Tape trading list upon request. SASE required for international mail.

From fstewart@demon.co.uk Sat Oct 14 10:38:57 1995
Path: ashpoly!cascade!transat!eunet-fr!teletel!demon!fstewart
From: fstewart@demon.co.uk (Fiona Stewart)
Newsgroups: comp.dsp
Subject: Re: [FLAME] Fixed-point Q15 arithmetic on Motorola DSP56001 vs IEEE floating point
Message-ID: <1995Oct14.103857.2250@demon.co.uk>
Date: Sat, 14 Oct 1995 10:38:57 GMT
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In article <1995Oct13.051157.9443@earthlink.net>, ysantos@earthlink.net (Yuki Santos) writes:
> Optimizing the Stardust Costas loop demodulator for the Motorola DSP56001 chip.
> However, when downsampling from 44.1 kHz to 64 Hz, accumulator overflow in the biquad IIR filter can destabilize the loop.

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

Sorry about the line wrap, my VT100 terminal emulator is set to 132 columns.

-- 
=== Fiona Stewart ===
Dept of Electrical Engineering, Demon Internet Services UK
"A soul is not exclusive to biology."

From csuzuki@berkeley.edu Sun Oct 15 00:56:57 1995
Path: ashpoly!cascade!transat!eunet-de!hansebox!berkeley!csuzuki
From: csuzuki@berkeley.edu (Camila Suzuki)
Newsgroups: comp.dsp
Subject: Re: [FLAME] Fixed-point Q15 arithmetic on Motorola DSP56001 vs IEEE floating point
Message-ID: <1995Oct15.005657.2753@berkeley.edu>
Date: Sun, 15 Oct 1995 00:56:57 GMT
References: <1995Oct13.051157.9443@earthlink.net>
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In article <1995Oct13.051157.9443@earthlink.net>, ysantos@earthlink.net (Yuki Santos) writes:
> Optimizing the Stardust Costas loop demodulator for the Motorola DSP56001 chip.
> However, when downsampling from 44.1 kHz to 64 Hz, accumulator overflow in the biquad IIR filter can destabilize the loop.

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

Netscape 1.1 crashes when loading large preformatted text. Stick to rn or tin!

-- 
Camila Suzuki | csuzuki@berkeley.edu
PGP Key fingerprint: D022 1FA3 4BC0 0742
"Keep the channels open."