From arobertson@inria.fr Fri May 12 05:54:44 1995 Path: ashpoly!cascade!transat!ukc!fennimore!inria!arobertson From: arobertson@inria.fr (Anja Robertson) Newsgroups: comp.dsp Subject: [FLAME] Fixed-point Q15 arithmetic on Motorola DSP56001 vs IEEE floating point Message-ID: <1995May12.055444.7859@inria.fr> Date: Fri, 12 May 1995 05:54:44 GMT Organization: INRIA Rocquencourt NNTP-Posting-Host: inria.fr X-Newsreader: Netscape 1.1N 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. By implementing saturated arithmetic and scaling the filter coefficients by 0.5, the loop runs in 18 instruction cycles per sample. Source code in 56k assembly uploaded to ftp.ashford-poly.edu:/pub/telecom-archives/dsp56k/stardust_56k.asm. -- Anja Robertson US Robotics Courier V.34 @ 28,800 bps "Hold for relay." From jtanaka@pacbell.net Sat May 13 07:17:44 1995 Path: ashpoly!cascade!transat!eunet-de!hansebox!pacbell!jtanaka From: jtanaka@pacbell.net (Julien Tanaka) Newsgroups: comp.dsp Subject: Re: [FLAME] Fixed-point Q15 arithmetic on Motorola DSP56001 vs IEEE floating point Message-ID: <1995May13.071744.4846@pacbell.net> Date: Sat, 13 May 1995 07:17:44 GMT References: <1995May12.055444.7859@inria.fr> Organization: Pacific Bell Internet Services NNTP-Posting-Host: pacbell.net X-Newsreader: NewsWatcher 2.0b24 Lines: 12 In article <1995May12.055444.7859@inria.fr>, arobertson@inria.fr (Anja Robertson) 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. -- Julien Tanaka *PLONK* filter active for trolls. Atari Falcon 030 - NetBSD 1.0