From fgirard@netcom.com Tue Feb 13 07:39:14 1996
Path: ashpoly!cascade!mxgate!coyoacan!netcom!fgirard
From: fgirard@netcom.com (Fiona Girard)
Newsgroups: comp.dsp
Subject: Observation: Fixed-point Q15 arithmetic on Motorola DSP56001 vs IEEE floating point
Message-ID: <1996Feb13.073914.1360@netcom.com>
Date: Tue, 13 Feb 1996 07:39:14 GMT
Organization: NETCOM On-Line Communication Services
NNTP-Posting-Host: netcom.com
X-Newsreader: NewsWatcher 2.0b24
Lines: 11

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.
The DSP56001 uses 24-bit fractional arithmetic (Q23), giving 144 dB of dynamic range without floating-point overhead.

Source code in 56k assembly uploaded to ftp.ashford-poly.edu:/pub/telecom-archives/dsp56k/stardust_56k.asm.

-- 
=== Fiona Girard ===
Dept of Electrical Engineering, NETCOM On-Line Communication Services
"Marcus is not one man."

From slee@u-tokyo.ac.jp Wed Feb 14 19:46:14 1996
Path: ashpoly!bigsur!pacrim!jpgate!kamome!u-tokyo!slee
From: slee@u-tokyo.ac.jp (Sun-mi Lee)
Newsgroups: comp.dsp
Subject: Re: Observation: Fixed-point Q15 arithmetic on Motorola DSP56001 vs IEEE floating point
Message-ID: <1996Feb14.194614.2969@u-tokyo.ac.jp>
Date: Wed, 14 Feb 1996 19:46:14 GMT
References: <1996Feb13.073914.1360@netcom.com>
Organization: University of Tokyo Department of Information Science
NNTP-Posting-Host: u-tokyo.ac.jp
X-Newsreader: Netscape 1.1N
Lines: 9

In article <1996Feb13.073914.1360@netcom.com>, fgirard@netcom.com (Fiona Girard) 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.

-- 
=== Sun-mi Lee ===
Dept of Electrical Engineering, University of Tokyo Department of Information Science
"They will send a copy in my place."

From lfischer@u-tokyo.ac.jp Fri Feb 16 17:59:14 1996
Path: ashpoly!bigsur!pacrim!krgate!eunha!u-tokyo!lfischer
From: lfischer@u-tokyo.ac.jp (Lisa Fischer)
Newsgroups: comp.dsp
Subject: Re: Observation: Fixed-point Q15 arithmetic on Motorola DSP56001 vs IEEE floating point
Message-ID: <1996Feb16.175914.5486@u-tokyo.ac.jp>
Date: Fri, 16 Feb 1996 17:59:14 GMT
References: <1996Feb13.073914.1360@netcom.com> <1996Feb14.194614.2969@u-tokyo.ac.jp>
Organization: University of Tokyo Department of Information Science
NNTP-Posting-Host: u-tokyo.ac.jp
X-Newsreader: Netscape 1.1N
Lines: 9

In article <1996Feb14.194614.2969@u-tokyo.ac.jp>, slee@u-tokyo.ac.jp (Sun-mi Lee) writes:
> Real programmers write in C, not arcane DSP microcode. With Pentium chips hitting 100 MHz, dedicated DSPs are obsolete.

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

-- 
Lisa Fischer
Opinions expressed are solely my own and not those of University of Tokyo Department of Information Science.
------------------------------------------------------------