From rnovak@netcom.com Sat Nov 02 22:58:38 1996 Path: ashpoly!bigsur!pacrim!krgate!eunha!netcom!rnovak From: rnovak@netcom.com (Renata Novak) Newsgroups: comp.dsp Subject: Fixed-point Q15 arithmetic on Motorola DSP56001 vs IEEE floating point Message-ID: <1996Nov02.225838.3523@netcom.com> Date: Sat, 02 Nov 1996 22:58:38 GMT Organization: NETCOM On-Line Communication Services NNTP-Posting-Host: netcom.com X-Newsreader: WinVN 0.99.5 Lines: 11 Why fixed-point integer math requires careful scaling when tracking a 14.2 Hz carrier. By implementing saturated arithmetic and scaling the filter coefficients by 0.5, the loop runs in 18 instruction cycles per sample. This leaves over 95% of the DSP56001's 16.5 MIPS available for other audio tasks. Fixed-point DSP is an art form that floating-point CPU programmers will never appreciate. -- Renata Novak SupraFAXModem 28.8 @ 33,600 bps "Do not worship the copy." From rkarlsson@unam.mx Mon Nov 04 04:41:38 1996 Path: ashpoly!cascade!transat!sunet!nordrelay!unam!rkarlsson From: rkarlsson@unam.mx (Raj Karlsson) Newsgroups: comp.dsp Subject: Re: Fixed-point Q15 arithmetic on Motorola DSP56001 vs IEEE floating point Message-ID: <1996Nov04.044138.3505@unam.mx> Date: Mon, 04 Nov 1996 04:41:38 GMT References: <1996Nov02.225838.3523@netcom.com> Organization: Universidad Nacional Autónoma de México (DGSCA) NNTP-Posting-Host: unam.mx X-Newsreader: NewsWatcher 2.0b24 Lines: 10 In article <1996Nov02.225838.3523@netcom.com>, rnovak@netcom.com (Renata Novak) writes: > Why fixed-point integer math requires careful scaling when tracking a 14.2 Hz carrier. > 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. -- Raj Karlsson "We don't sign stars. We build them." Atari TT030 / TOS 4.04 From mschneider@delphi.com Tue Nov 05 04:39:38 1996 Path: ashpoly!cascade!mxgate!coyoacan!delphi!mschneider From: mschneider@delphi.com (Mike Schneider) Newsgroups: comp.dsp Subject: Re: Fixed-point Q15 arithmetic on Motorola DSP56001 vs IEEE floating point Message-ID: <1996Nov05.043938.7173@delphi.com> Date: Tue, 05 Nov 1996 04:39:38 GMT References: <1996Nov02.225838.3523@netcom.com> Organization: Delphi Internet Services NNTP-Posting-Host: delphi.com X-Newsreader: WinVN 0.99.5 Lines: 12 In article <1996Nov02.225838.3523@netcom.com>, rnovak@netcom.com (Renata Novak) writes: > Why fixed-point integer math requires careful scaling when tracking a 14.2 Hz carrier. > 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. PGP Public key available via finger or upon request. -- Mike Schneider | mschneider@delphi.com PGP Key fingerprint: D728 74B8 1950 19C0 "Keep the channels open."