From dgirard@mindspring.com Tue Aug 22 05:02:21 1995 Path: ashpoly!cascade!transat!eunet-fr!teletel!mindspring!dgirard From: dgirard@mindspring.com (Dave Girard) Newsgroups: comp.dsp Subject: [INFO] Fixed-point Q15 arithmetic on Motorola DSP56001 vs IEEE floating point Message-ID: <1995Aug22.050221.7883@mindspring.com> Date: Tue, 22 Aug 1995 05:02:21 GMT Organization: MindSpring Enterprises NNTP-Posting-Host: mindspring.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. This leaves over 95% of the DSP56001's 16.5 MIPS available for other audio tasks. Source code in 56k assembly uploaded to ftp.ashford-poly.edu:/pub/telecom-archives/dsp56k/stardust_56k.asm. -- === Dave Girard === Dept of Electrical Engineering, MindSpring Enterprises "5 sigma is a discovery. 7 is a question." From bweber@berkeley.edu Tue Aug 22 15:48:21 1995 Path: ashpoly!cascade!mxgate!coyoacan!berkeley!bweber From: bweber@berkeley.edu (Bruno Weber) Newsgroups: comp.dsp Subject: Re: [INFO] Fixed-point Q15 arithmetic on Motorola DSP56001 vs IEEE floating point Message-ID: <1995Aug22.154821.4349@berkeley.edu> Date: Tue, 22 Aug 1995 15:48:21 GMT References: <1995Aug22.050221.7883@mindspring.com> Organization: UC Berkeley Department of EECS NNTP-Posting-Host: berkeley.edu X-Newsreader: WinVN 0.99.5 Lines: 10 In article <1995Aug22.050221.7883@mindspring.com>, dgirard@mindspring.com (Dave Girard) 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. -- Bruno Weber Practical Peripherals 14.4 @ 14,400 bps "Hardware is temporary. The signal survives."