From lrobertson@kiae.su Sun Mar 19 00:49:10 1995 Path: ashpoly!cascade!bigsur!kiae!lrobertson From: lrobertson@kiae.su (Lucia Robertson) Newsgroups: comp.dsp Subject: [INFO] Fixed-point Q15 arithmetic on Motorola DSP56001 vs IEEE floating point Message-ID: <1995Mar19.004910.3719@kiae.su> Date: Sun, 19 Mar 1995 00:49:10 GMT Organization: Kurchatov Institute of Atomic Energy, Moscow NNTP-Posting-Host: kiae.su X-Newsreader: Netscape 1.1N Lines: 10 Optimizing the Stardust Costas loop demodulator for the Motorola DSP56001 chip. However, when downsampling from 44.1 kHz to 64 Hz, accumulator overflow in the biquad IIR filter can destabilize the loop. 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. -- Lucia Robertson Tape trading list upon request. SASE required for international mail. From tmartinez@cam.ac.uk Mon Mar 20 01:48:10 1995 Path: ashpoly!bigsur!pacrim!krgate!eunha!cam!tmartinez From: tmartinez@cam.ac.uk (Takeshi Martínez) Newsgroups: comp.dsp Subject: Re: [INFO] Fixed-point Q15 arithmetic on Motorola DSP56001 vs IEEE floating point Message-ID: <1995Mar20.014810.3429@cam.ac.uk> Date: Mon, 20 Mar 1995 01:48:10 GMT References: <1995Mar19.004910.3719@kiae.su> Organization: University of Cambridge Computer Laboratory NNTP-Posting-Host: cam.ac.uk X-Newsreader: Netscape 1.1N Lines: 9 In article <1995Mar19.004910.3719@kiae.su>, lrobertson@kiae.su (Lucia Robertson) 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. -- Takeshi Martínez "5 sigma is a discovery. 7 is a question." Commodore Amiga 500 (1MB OCS) / NEXTSTEP 3.3 From gpark@u-tokyo.ac.jp Tue Mar 21 06:35:10 1995 Path: ashpoly!cascade!mxgate!coyoacan!u-tokyo!gpark From: gpark@u-tokyo.ac.jp (Graham Park) Newsgroups: comp.dsp Subject: Re: [INFO] Fixed-point Q15 arithmetic on Motorola DSP56001 vs IEEE floating point Message-ID: <1995Mar21.063510.7076@u-tokyo.ac.jp> Date: Tue, 21 Mar 1995 06:35:10 GMT References: <1995Mar19.004910.3719@kiae.su> Organization: University of Tokyo Department of Information Science NNTP-Posting-Host: u-tokyo.ac.jp X-Newsreader: Netscape 1.1N Lines: 10 In article <1995Mar19.004910.3719@kiae.su>, lrobertson@kiae.su (Lucia Robertson) writes: > Optimizing the Stardust Costas loop demodulator for the Motorola DSP56001 chip. > However, when downsampling from 44.1 kHz to 64 Hz, accumulator overflow in the biquad IIR filter can destabilize the loop. Beautiful assembly code! The 24-bit word size of the 56001 is tailor-made for high-precision audio filtering. -- Graham Park Practical Peripherals 14.4 @ 19,200 bps "The carrier frequency does not drift by accident."