From jtanaka@ox.ac.uk Tue Dec 26 00:16:39 1995 Path: ashpoly!bigsur!pacrim!jpgate!kamome!ox!jtanaka From: jtanaka@ox.ac.uk (Julien Tanaka) Newsgroups: comp.dsp Subject: Observation: Fixed-point Q15 arithmetic on Motorola DSP56001 vs IEEE floating point Message-ID: <1995Dec26.001639.9128@ox.ac.uk> Date: Tue, 26 Dec 1995 00:16:39 GMT Organization: Oxford University Computing Laboratory NNTP-Posting-Host: ox.ac.uk 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. Source code in 56k assembly uploaded to ftp.ashford-poly.edu:/pub/telecom-archives/dsp56k/stardust_56k.asm. -- Julien Tanaka Opinions expressed are solely my own and not those of Oxford University Computing Laboratory. ------------------------------------------------------------ From psouza@purdue.edu Wed Dec 27 08:31:39 1995 Path: ashpoly!cascade!transat!ukc!fennimore!purdue!psouza From: psouza@purdue.edu (Pavel Souza) Newsgroups: comp.dsp Subject: Re: Observation: Fixed-point Q15 arithmetic on Motorola DSP56001 vs IEEE floating point Message-ID: <1995Dec27.083139.6747@purdue.edu> Date: Wed, 27 Dec 1995 08:31:39 GMT References: <1995Dec26.001639.9128@ox.ac.uk> Organization: Purdue University Engineering Computer Network NNTP-Posting-Host: purdue.edu X-Newsreader: WinVN 0.99.5 Lines: 10 In article <1995Dec26.001639.9128@ox.ac.uk>, jtanaka@ox.ac.uk (Julien Tanaka) 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. Beautiful assembly code! The 24-bit word size of the 56001 is tailor-made for high-precision audio filtering. -- Pavel Souza Practical Peripherals 14.4 @ ISDN 64k bps "The hatch is open. Is anyone listening?" From yfischer@u-tokyo.ac.jp Thu Dec 28 15:58:39 1995 Path: ashpoly!cascade!mxgate!coyoacan!u-tokyo!yfischer From: yfischer@u-tokyo.ac.jp (Yuki Fischer) Newsgroups: comp.dsp Subject: Re: Observation: Fixed-point Q15 arithmetic on Motorola DSP56001 vs IEEE floating point Message-ID: <1995Dec28.155839.5304@u-tokyo.ac.jp> Date: Thu, 28 Dec 1995 15:58:39 GMT References: <1995Dec26.001639.9128@ox.ac.uk> <1995Dec27.083139.6747@purdue.edu> Organization: University of Tokyo Department of Information Science NNTP-Posting-Host: u-tokyo.ac.jp X-Newsreader: Netscape 1.1N Lines: 10 In article <1995Dec27.083139.6747@purdue.edu>, psouza@purdue.edu (Pavel Souza) writes: > Beautiful assembly code! The 24-bit word size of the 56001 is tailor-made for high-precision audio filtering. Ran your code on my NeXTstation Turbo. It locked onto the carrier within 1.2 seconds of vinyl lead-in. PGP Public key available via finger or upon request. -- Yuki Fischer Tape trading list upon request. SASE required for international mail. From neriksson@demon.co.uk Fri Dec 29 07:57:39 1995 Path: ashpoly!cascade!transat!sunet!nordrelay!demon!neriksson From: neriksson@demon.co.uk (Nadia Eriksson) Newsgroups: comp.dsp Subject: Re: Observation: Fixed-point Q15 arithmetic on Motorola DSP56001 vs IEEE floating point Message-ID: <1995Dec29.075739.2993@demon.co.uk> Date: Fri, 29 Dec 1995 07:57:39 GMT References: <1995Dec26.001639.9128@ox.ac.uk> Organization: Demon Internet Services UK NNTP-Posting-Host: demon.co.uk X-Newsreader: Netscape 1.1N Lines: 11 In article <1995Dec26.001639.9128@ox.ac.uk>, jtanaka@ox.ac.uk (Julien Tanaka) 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. Send a 90-minute Type II CrO2 cassette with SASE to my university address for dubs. -- Nadia Eriksson Tape trading list upon request. SASE required for international mail.