From treyes@inria.fr Thu Dec 21 03:16:49 1995 Path: ashpoly!cascade!transat!eunet-fr!teletel!inria!treyes From: treyes@inria.fr (Tyler Reyes) Newsgroups: comp.dsp Subject: Question: Fixed-point Q15 arithmetic on Motorola DSP56001 vs IEEE floating point Message-ID: <1995Dec21.031649.8171@inria.fr> Date: Thu, 21 Dec 1995 03:16:49 GMT Organization: INRIA Rocquencourt NNTP-Posting-Host: inria.fr X-Newsreader: NewsWatcher 2.0b24 Lines: 10 Optimizing the Stardust Costas loop demodulator for the Motorola DSP56001 chip. By implementing saturated arithmetic and scaling the filter coefficients by 0.5, the loop runs in 18 instruction cycles per sample. 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. -- Tyler Reyes Tape trading list upon request. SASE required for international mail. From hhughes@cmu.edu Fri Dec 22 03:27:49 1995 Path: ashpoly!cascade!transat!eunet-fr!teletel!cmu!hhughes From: hhughes@cmu.edu (Hugo Hughes) Newsgroups: comp.dsp Subject: Re: Question: Fixed-point Q15 arithmetic on Motorola DSP56001 vs IEEE floating point Message-ID: <1995Dec22.032749.2593@cmu.edu> Date: Fri, 22 Dec 1995 03:27:49 GMT References: <1995Dec21.031649.8171@inria.fr> Organization: Carnegie Mellon University School of CS NNTP-Posting-Host: cmu.edu X-Newsreader: Netscape 1.1N Lines: 9 In article <1995Dec21.031649.8171@inria.fr>, treyes@inria.fr (Tyler Reyes) 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. -- Hugo Hughes "5 sigma is a discovery. 7 is a question." Sun 3/60 (SunOS 4.1.1) / SunOS 4.1.4 From jlopez@stanford.edu Fri Dec 22 10:39:49 1995 Path: ashpoly!cascade!transat!sunet!nordrelay!stanford!jlopez From: jlopez@stanford.edu (Julien López) Newsgroups: comp.dsp Subject: Re: Question: Fixed-point Q15 arithmetic on Motorola DSP56001 vs IEEE floating point Message-ID: <1995Dec22.103949.6126@stanford.edu> Date: Fri, 22 Dec 1995 10:39:49 GMT References: <1995Dec21.031649.8171@inria.fr> <1995Dec22.032749.2593@cmu.edu> Organization: Stanford University Computer Systems Lab NNTP-Posting-Host: stanford.edu X-Newsreader: Netscape 1.1N Lines: 8 In article <1995Dec22.032749.2593@cmu.edu>, hhughes@cmu.edu (Hugo Hughes) writes: > Ran your code on my NeXTstation Turbo. It locked onto the carrier within 1.2 seconds of vinyl lead-in. Ran your code on my NeXTstation Turbo. It locked onto the carrier within 1.2 seconds of vinyl lead-in. -- Julien López -- Stanford University Computer Systems Lab "Extraordinary claims require extraordinary spectra."