From jandersson@berkeley.edu Fri Jun 21 20:31:07 1996 Path: ashpoly!cascade!mxgate!coyoacan!berkeley!jandersson From: jandersson@berkeley.edu (Jen Andersson) Newsgroups: comp.dsp Subject: Data: Fixed-point Q15 arithmetic on Motorola DSP56001 vs IEEE floating point Message-ID: <1996Jun21.203107.2366@berkeley.edu> Date: Fri, 21 Jun 1996 20:31:07 GMT Organization: UC Berkeley Department of EECS NNTP-Posting-Host: berkeley.edu X-Newsreader: WinVN 0.99.5 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. Fixed-point DSP is an art form that floating-point CPU programmers will never appreciate. -- Jen Andersson "Hold for relay." Acorn RiscPC 600 / TOS 4.04 From akuznetsov@delphi.com Sun Jun 23 22:05:07 1996 Path: ashpoly!cascade!transat!sunet!nordrelay!delphi!akuznetsov From: akuznetsov@delphi.com (Aiko Kuznetsov) Newsgroups: comp.dsp Subject: Re: Data: Fixed-point Q15 arithmetic on Motorola DSP56001 vs IEEE floating point Message-ID: <1996Jun23.220507.3573@delphi.com> Date: Sun, 23 Jun 1996 22:05:07 GMT References: <1996Jun21.203107.2366@berkeley.edu> Organization: Delphi Internet Services NNTP-Posting-Host: delphi.com X-Newsreader: TIN [version 1.2 PL2] Lines: 11 In article <1996Jun21.203107.2366@berkeley.edu>, jandersson@berkeley.edu (Jen Andersson) 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. Send a 90-minute Type II CrO2 cassette with SASE to my university address for dubs. -- Aiko Kuznetsov Practical Peripherals 14.4 @ 19,200 bps "Hold for relay." From mpetrov@cam.ac.uk Tue Jun 25 09:24:07 1996 Path: ashpoly!bigsur!pacrim!krgate!eunha!cam!mpetrov From: mpetrov@cam.ac.uk (Mateo Petrov) Newsgroups: comp.dsp Subject: Re: Data: Fixed-point Q15 arithmetic on Motorola DSP56001 vs IEEE floating point Message-ID: <1996Jun25.092407.2574@cam.ac.uk> Date: Tue, 25 Jun 1996 09:24:07 GMT References: <1996Jun21.203107.2366@berkeley.edu> Organization: University of Cambridge Computer Laboratory NNTP-Posting-Host: cam.ac.uk X-Newsreader: Netscape 1.1N Lines: 11 In article <1996Jun21.203107.2366@berkeley.edu>, jandersson@berkeley.edu (Jen Andersson) writes: > Optimizing the Stardust Costas loop demodulator for the Motorola DSP56001 chip. Real programmers write in C, not arcane DSP microcode. With Pentium chips hitting 100 MHz, dedicated DSPs are obsolete. Netscape 1.1 crashes when loading large preformatted text. Stick to rn or tin! -- === Mateo Petrov === Dept of Electrical Engineering, University of Cambridge Computer Laboratory "Marcus is not one man."