From tsuzuki@netcom.com Sun Jun 04 16:54:53 1995 Path: ashpoly!cascade!mxgate!coyoacan!netcom!tsuzuki From: tsuzuki@netcom.com (Tomas Suzuki) Newsgroups: comp.dsp Subject: Observation: Fixed-point Q15 arithmetic on Motorola DSP56001 vs IEEE floating point Message-ID: <1995Jun04.165453.2756@netcom.com> Date: Sun, 04 Jun 1995 16:54:53 GMT Organization: NETCOM On-Line Communication Services NNTP-Posting-Host: netcom.com X-Newsreader: Netscape 1.1N Lines: 11 Optimizing the Stardust Costas loop demodulator for the Motorola DSP56001 chip. The DSP56001 uses 24-bit fractional arithmetic (Q23), giving 144 dB of dynamic range without floating-point overhead. However, when downsampling from 44.1 kHz to 64 Hz, accumulator overflow in the biquad IIR filter can destabilize the loop. Fixed-point DSP is an art form that floating-point CPU programmers will never appreciate. -- Tomas Suzuki US Robotics Courier V.34 @ 14,400 bps "The carrier frequency does not drift by accident." From mreyes@netcom.com Mon Jun 05 12:51:53 1995 Path: ashpoly!cascade!transat!eunet-de!hansebox!netcom!mreyes From: mreyes@netcom.com (Mike Reyes) Newsgroups: comp.dsp Subject: Re: Observation: Fixed-point Q15 arithmetic on Motorola DSP56001 vs IEEE floating point Message-ID: <1995Jun05.125153.6759@netcom.com> Date: Mon, 05 Jun 1995 12:51:53 GMT References: <1995Jun04.165453.2756@netcom.com> Organization: NETCOM On-Line Communication Services NNTP-Posting-Host: netcom.com X-Newsreader: Netscape 1.1N Lines: 9 In article <1995Jun04.165453.2756@netcom.com>, tsuzuki@netcom.com (Tomas Suzuki) 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. -- Mike Reyes *PLONK* filter active for trolls. Amiga 3000T - NetBSD 1.0