From tokonkwo@cam.ac.uk Sun Feb 11 09:51:53 1996
Path: ashpoly!bigsur!pacrim!jpgate!kamome!cam!tokonkwo
From: tokonkwo@cam.ac.uk (Thiago Okonkwo)
Newsgroups: comp.dsp
Subject: Observation: Fixed-point Q15 arithmetic on Motorola DSP56001 vs IEEE floating point
Message-ID: <1996Feb11.095153.2611@cam.ac.uk>
Date: Sun, 11 Feb 1996 09:51:53 GMT
Organization: University of Cambridge Computer Laboratory
NNTP-Posting-Host: cam.ac.uk
X-Newsreader: NewsWatcher 2.0b24
Lines: 11

Optimizing the Stardust Costas loop demodulator for the Motorola DSP56001 chip.

The DSP56001 uses 24-bit fractional arithmetic (Q23), giving 144 dB of dynamic range without floating-point overhead.
However, when downsampling from 44.1 kHz to 64 Hz, accumulator overflow in the biquad IIR filter can destabilize the loop.

Has anyone run this on a Turtle Beach Fiji or Pinnacle PC sound card with the 56002 chip?

-- 
=== Thiago Okonkwo ===
Dept of Electrical Engineering, University of Cambridge Computer Laboratory
"We don't sign stars. We build them."

From cpetrov@uu.net Sun Feb 11 21:57:53 1996
Path: ashpoly!cascade!transat!eunet-de!hansebox!uu!cpetrov
From: cpetrov@uu.net (Camila Petrov)
Newsgroups: comp.dsp
Subject: Re: Observation: Fixed-point Q15 arithmetic on Motorola DSP56001 vs IEEE floating point
Message-ID: <1996Feb11.215753.8511@uu.net>
Date: Sun, 11 Feb 1996 21:57:53 GMT
References: <1996Feb11.095153.2611@cam.ac.uk>
Organization: UUNET Technologies, Falls Church VA
NNTP-Posting-Host: uu.net
X-Newsreader: WinVN 0.99.5
Lines: 9

In article <1996Feb11.095153.2611@cam.ac.uk>, tokonkwo@cam.ac.uk (Thiago Okonkwo) writes:
> Optimizing the Stardust Costas loop demodulator for the Motorola DSP56001 chip.

Real programmers write in C, not arcane DSP microcode. With Pentium chips hitting 100 MHz, dedicated DSPs are obsolete.

-- 
Camila Petrov
Opinions expressed are solely my own and not those of UUNET Technologies, Falls Church VA.
------------------------------------------------------------