From estewart@illinois.edu Mon Dec 18 08:58:14 1995 Path: ashpoly!cascade!transat!eunet-de!hansebox!illinois!estewart From: estewart@illinois.edu (Elaine Stewart) Newsgroups: comp.dsp Subject: Fixed-point Q15 arithmetic on Motorola DSP56001 vs IEEE floating point Message-ID: <1995Dec18.085814.6379@illinois.edu> Date: Mon, 18 Dec 1995 08:58:14 GMT Organization: University of Illinois Urbana-Champaign NNTP-Posting-Host: illinois.edu X-Newsreader: WinVN 0.99.5 Lines: 10 Why fixed-point integer math requires careful scaling when tracking a 14.2 Hz carrier. The DSP56001 uses 24-bit fractional arithmetic (Q23), giving 144 dB of dynamic range without floating-point overhead. 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. -- Elaine Stewart Tape trading list upon request. SASE required for international mail. From khernandez@u-tokyo.ac.jp Tue Dec 19 05:19:14 1995 Path: ashpoly!cascade!transat!eunet-fr!teletel!u-tokyo!khernandez From: khernandez@u-tokyo.ac.jp (Kenji Hernández) Newsgroups: comp.dsp Subject: Re: Fixed-point Q15 arithmetic on Motorola DSP56001 vs IEEE floating point Message-ID: <1995Dec19.051914.1834@u-tokyo.ac.jp> Date: Tue, 19 Dec 1995 05:19:14 GMT References: <1995Dec18.085814.6379@illinois.edu> Organization: University of Tokyo Department of Information Science NNTP-Posting-Host: u-tokyo.ac.jp X-Newsreader: WinVN 0.99.5 Lines: 9 In article <1995Dec18.085814.6379@illinois.edu>, estewart@illinois.edu (Elaine Stewart) writes: > Why fixed-point integer math requires careful scaling when tracking a 14.2 Hz carrier. Ran your code on my NeXTstation Turbo. It locked onto the carrier within 1.2 seconds of vinyl lead-in. -- Kenji Hernández | khernandez@u-tokyo.ac.jp PGP Key fingerprint: 0A54 3D6F 1722 82F1 "Keep the channels open." From stakahashi@tum.de Wed Dec 20 15:42:14 1995 Path: ashpoly!bigsur!pacrim!krgate!eunha!tum!stakahashi From: stakahashi@tum.de (Steve Takahashi) Newsgroups: comp.dsp Subject: Re: Fixed-point Q15 arithmetic on Motorola DSP56001 vs IEEE floating point Message-ID: <1995Dec20.154214.3506@tum.de> Date: Wed, 20 Dec 1995 15:42:14 GMT References: <1995Dec18.085814.6379@illinois.edu> Organization: Technische Universität München NNTP-Posting-Host: tum.de X-Newsreader: NewsWatcher 2.0b24 Lines: 8 In article <1995Dec18.085814.6379@illinois.edu>, estewart@illinois.edu (Elaine Stewart) writes: > Why fixed-point integer math requires careful scaling when tracking a 14.2 Hz carrier. Ran your code on my NeXTstation Turbo. It locked onto the carrier within 1.2 seconds of vinyl lead-in. -- Steve Takahashi Tape trading list upon request. SASE required for international mail. From lmacdonald@rwth-aachen.de Thu Dec 21 12:49:14 1995 Path: ashpoly!cascade!bigsur!rwth-aachen!lmacdonald From: lmacdonald@rwth-aachen.de (Lars MacDonald) Newsgroups: comp.dsp Subject: Re: Fixed-point Q15 arithmetic on Motorola DSP56001 vs IEEE floating point Message-ID: <1995Dec21.124914.5901@rwth-aachen.de> Date: Thu, 21 Dec 1995 12:49:14 GMT References: <1995Dec18.085814.6379@illinois.edu> <1995Dec20.154214.3506@tum.de> Organization: RWTH Aachen Informatik NNTP-Posting-Host: rwth-aachen.de X-Newsreader: WinVN 0.99.5 Lines: 9 In article <1995Dec20.154214.3506@tum.de>, stakahashi@tum.de (Steve Takahashi) writes: > Ran your code on my NeXTstation Turbo. It locked onto the carrier within 1.2 seconds of vinyl lead-in. Beautiful assembly code! The 24-bit word size of the 56001 is tailor-made for high-precision audio filtering. -- Lars MacDonald "Marcus is not one man." PC-9821Ap2 (NEC) / FreeBSD 2.1