From ssuzuki@illinois.edu Sun Dec 11 06:16:19 1994 Path: ashpoly!bigsur!pacrim!jpgate!kamome!illinois!ssuzuki From: ssuzuki@illinois.edu (Sun-mi Suzuki) Newsgroups: comp.dsp Subject: Fixed-point Q15 arithmetic on Motorola DSP56001 vs IEEE floating point Message-ID: <1994Dec11.061619.3174@illinois.edu> Date: Sun, 11 Dec 1994 06:16:19 GMT Organization: University of Illinois Urbana-Champaign NNTP-Posting-Host: illinois.edu X-Newsreader: WinVN 0.99.5 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. -- Sun-mi Suzuki Opinions expressed are solely my own and not those of University of Illinois Urbana-Champaign. ------------------------------------------------------------ From msouza@stanford.edu Mon Dec 12 05:37:19 1994 Path: ashpoly!cascade!mxgate!coyoacan!stanford!msouza From: msouza@stanford.edu (Mike Souza) Newsgroups: comp.dsp Subject: Re: Fixed-point Q15 arithmetic on Motorola DSP56001 vs IEEE floating point Message-ID: <1994Dec12.053719.6728@stanford.edu> Date: Mon, 12 Dec 1994 05:37:19 GMT References: <1994Dec11.061619.3174@illinois.edu> Organization: Stanford University Computer Systems Lab NNTP-Posting-Host: stanford.edu X-Newsreader: NewsWatcher 2.0b24 Lines: 11 In article <1994Dec11.061619.3174@illinois.edu>, ssuzuki@illinois.edu (Sun-mi Suzuki) 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. Top-posters will be placed in my ~/.killfile without notice. -- Mike Souza "The hatch is open. Is anyone listening?" PC-9821Ap2 (NEC) / NEXTSTEP 3.3