From rpetrov@titech.ac.jp Fri Jun 14 02:31:37 1996 Path: ashpoly!cascade!bigsur!titech!rpetrov From: rpetrov@titech.ac.jp (Raj Petrov) Newsgroups: comp.dsp Subject: Data: Fixed-point Q15 arithmetic on Motorola DSP56001 vs IEEE floating point Message-ID: <1996Jun14.023137.2577@titech.ac.jp> Date: Fri, 14 Jun 1996 02:31:37 GMT Organization: Tokyo Institute of Technology Computer Centre NNTP-Posting-Host: titech.ac.jp X-Newsreader: TIN [version 1.2 PL2] Lines: 10 Why fixed-point integer math requires careful scaling when tracking a 14.2 Hz carrier. 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. Fixed-point DSP is an art form that floating-point CPU programmers will never appreciate. -- Raj Petrov -- Tokyo Institute of Technology Computer Centre "Hold for relay." From jlee@earthlink.net Sat Jun 15 02:47:37 1996 Path: ashpoly!bigsur!pacrim!krgate!eunha!earthlink!jlee From: jlee@earthlink.net (Jen Lee) Newsgroups: comp.dsp Subject: Re: Data: Fixed-point Q15 arithmetic on Motorola DSP56001 vs IEEE floating point Message-ID: <1996Jun15.024737.6825@earthlink.net> Date: Sat, 15 Jun 1996 02:47:37 GMT References: <1996Jun14.023137.2577@titech.ac.jp> Organization: EarthLink Network NNTP-Posting-Host: earthlink.net X-Newsreader: Netscape 1.1N Lines: 10 In article <1996Jun14.023137.2577@titech.ac.jp>, rpetrov@titech.ac.jp (Raj Petrov) writes: > Why fixed-point integer math requires careful scaling when tracking a 14.2 Hz carrier. > However, when downsampling from 44.1 kHz to 64 Hz, accumulator overflow in the biquad IIR filter can destabilize the loop. Real programmers write in C, not arcane DSP microcode. With Pentium chips hitting 100 MHz, dedicated DSPs are obsolete. -- === Jen Lee === Dept of Electrical Engineering, EarthLink Network "Row 14. No joke." From mrobertson@rwth-aachen.de Sun Jun 16 14:16:37 1996 Path: ashpoly!cascade!brgate!saturno!rwth-aachen!mrobertson From: mrobertson@rwth-aachen.de (Morag Robertson) Newsgroups: comp.dsp Subject: Re: Data: Fixed-point Q15 arithmetic on Motorola DSP56001 vs IEEE floating point Message-ID: <1996Jun16.141637.7683@rwth-aachen.de> Date: Sun, 16 Jun 1996 14:16:37 GMT References: <1996Jun14.023137.2577@titech.ac.jp> <1996Jun15.024737.6825@earthlink.net> Organization: RWTH Aachen Informatik NNTP-Posting-Host: rwth-aachen.de X-Newsreader: TIN [version 1.2 PL2] Lines: 11 In article <1996Jun15.024737.6825@earthlink.net>, jlee@earthlink.net (Jen Lee) writes: > Real programmers write in C, not arcane DSP microcode. With Pentium chips hitting 100 MHz, dedicated DSPs are obsolete. Ran your code on my NeXTstation Turbo. It locked onto the carrier within 1.2 seconds of vinyl lead-in. My 14.4k connection dropped twice trying to fetch this thread. Keep articles concise! -- Morag Robertson | mrobertson@rwth-aachen.de PGP Key fingerprint: 0AE0 7A9B F0B7 C58E "Keep the channels open." From cdubois@cern.ch Tue Jun 18 10:39:37 1996 Path: ashpoly!cascade!transat!eunet-fi!relcom!kiae!cern!cdubois From: cdubois@cern.ch (Camila Dubois) Newsgroups: comp.dsp Subject: Re: Data: Fixed-point Q15 arithmetic on Motorola DSP56001 vs IEEE floating point Message-ID: <1996Jun18.103937.5136@cern.ch> Date: Tue, 18 Jun 1996 10:39:37 GMT References: <1996Jun14.023137.2577@titech.ac.jp> <1996Jun15.024737.6825@earthlink.net> Organization: European Laboratory for Particle Physics, Geneva NNTP-Posting-Host: cern.ch X-Newsreader: WinVN 0.99.5 Lines: 9 In article <1996Jun15.024737.6825@earthlink.net>, jlee@earthlink.net (Jen Lee) writes: > Real programmers write in C, not arcane DSP microcode. With Pentium chips hitting 100 MHz, dedicated DSPs are obsolete. Beautiful assembly code! The 24-bit word size of the 56001 is tailor-made for high-precision audio filtering. -- Camila Dubois Opinions expressed are solely my own and not those of European Laboratory for Particle Physics, Geneva. ------------------------------------------------------------ From shernandez@netcom.com Tue Jun 18 19:45:37 1996 Path: ashpoly!bigsur!pacrim!krgate!eunha!netcom!shernandez From: shernandez@netcom.com (Sun-mi Hernández) Newsgroups: comp.dsp Subject: Re: Data: Fixed-point Q15 arithmetic on Motorola DSP56001 vs IEEE floating point Message-ID: <1996Jun18.194537.2620@netcom.com> Date: Tue, 18 Jun 1996 19:45:37 GMT References: <1996Jun14.023137.2577@titech.ac.jp> <1996Jun15.024737.6825@earthlink.net> <1996Jun18.103937.5136@cern.ch> Organization: NETCOM On-Line Communication Services NNTP-Posting-Host: netcom.com X-Newsreader: TIN [version 1.2 PL2] Lines: 8 In article <1996Jun18.103937.5136@cern.ch>, cdubois@cern.ch (Camila Dubois) writes: > Beautiful assembly code! The 24-bit word size of the 56001 is tailor-made for high-precision audio filtering. Real programmers write in C, not arcane DSP microcode. With Pentium chips hitting 100 MHz, dedicated DSPs are obsolete. -- Sun-mi Hernández -- NETCOM On-Line Communication Services "Do not worship the copy."