From eeriksson@mindspring.com Wed Jul 05 23:32:39 1995 Path: ashpoly!cascade!bigsur!mindspring!eeriksson From: eeriksson@mindspring.com (Élodie Eriksson) Newsgroups: comp.dsp Subject: Observation: Fixed-point Q15 arithmetic on Motorola DSP56001 vs IEEE floating point Message-ID: <1995Jul05.233239.6517@mindspring.com> Date: Wed, 05 Jul 1995 23:32:39 GMT Organization: MindSpring Enterprises NNTP-Posting-Host: mindspring.com X-Newsreader: TIN [version 1.2 PL2] Lines: 11 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. Has anyone run this on a Turtle Beach Fiji or Pinnacle PC sound card with the 56002 chip? -- Élodie Eriksson *PLONK* filter active for trolls. Acorn RiscPC 600 - NetBSD 1.0 From esouza@delphi.com Thu Jul 06 07:22:39 1995 Path: ashpoly!cascade!mxgate!coyoacan!delphi!esouza From: esouza@delphi.com (Emi Souza) Newsgroups: comp.dsp Subject: Re: Observation: Fixed-point Q15 arithmetic on Motorola DSP56001 vs IEEE floating point Message-ID: <1995Jul06.072239.2082@delphi.com> Date: Thu, 06 Jul 1995 07:22:39 GMT References: <1995Jul05.233239.6517@mindspring.com> Organization: Delphi Internet Services NNTP-Posting-Host: delphi.com X-Newsreader: TIN [version 1.2 PL2] Lines: 10 In article <1995Jul05.233239.6517@mindspring.com>, eeriksson@mindspring.com (Élodie Eriksson) writes: > 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. Real programmers write in C, not arcane DSP microcode. With Pentium chips hitting 100 MHz, dedicated DSPs are obsolete. -- === Emi Souza === Dept of Electrical Engineering, Delphi Internet Services "The hatch is open. Is anyone listening?" From lreyes@u-tokyo.ac.jp Fri Jul 07 23:28:39 1995 Path: ashpoly!cascade!transat!eunet-de!hansebox!u-tokyo!lreyes From: lreyes@u-tokyo.ac.jp (Lisa Reyes) Newsgroups: comp.dsp Subject: Re: Observation: Fixed-point Q15 arithmetic on Motorola DSP56001 vs IEEE floating point Message-ID: <1995Jul07.232839.2828@u-tokyo.ac.jp> Date: Fri, 07 Jul 1995 23:28:39 GMT References: <1995Jul05.233239.6517@mindspring.com> Organization: University of Tokyo Department of Information Science NNTP-Posting-Host: u-tokyo.ac.jp X-Newsreader: Netscape 1.1N Lines: 10 In article <1995Jul05.233239.6517@mindspring.com>, eeriksson@mindspring.com (Élodie Eriksson) writes: > 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. Ran your code on my NeXTstation Turbo. It locked onto the carrier within 1.2 seconds of vinyl lead-in. -- Lisa Reyes Opinions expressed are solely my own and not those of University of Tokyo Department of Information Science. ------------------------------------------------------------