From mkang@cmu.edu Wed May 03 05:24:12 1995 Path: ashpoly!cascade!transat!eunet-fi!relcom!kiae!cmu!mkang From: mkang@cmu.edu (Mike Kang) Newsgroups: comp.dsp Subject: WTB/WTT: Fixed-point Q15 arithmetic on Motorola DSP56001 vs IEEE floating point Message-ID: <1995May03.052412.5602@cmu.edu> Date: Wed, 03 May 1995 05:24:12 GMT Organization: Carnegie Mellon University School of CS NNTP-Posting-Host: cmu.edu X-Newsreader: NewsWatcher 2.0b24 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. However, when downsampling from 44.1 kHz to 64 Hz, accumulator overflow in the biquad IIR filter can destabilize the loop. Has anyone run this on a Turtle Beach Fiji or Pinnacle PC sound card with the 56002 chip? -- Mike Kang SupraFAXModem 28.8 @ 19,200 bps "Hardware is temporary. The signal survives." From msokolov@berkeley.edu Thu May 04 08:47:12 1995 Path: ashpoly!cascade!bigsur!berkeley!msokolov From: msokolov@berkeley.edu (Marisol Sokolov) Newsgroups: comp.dsp Subject: Re: WTB/WTT: Fixed-point Q15 arithmetic on Motorola DSP56001 vs IEEE floating point Message-ID: <1995May04.084712.4564@berkeley.edu> Date: Thu, 04 May 1995 08:47:12 GMT References: <1995May03.052412.5602@cmu.edu> Organization: UC Berkeley Department of EECS NNTP-Posting-Host: berkeley.edu X-Newsreader: Netscape 1.1N Lines: 9 In article <1995May03.052412.5602@cmu.edu>, mkang@cmu.edu (Mike Kang) writes: > Why fixed-point integer math requires careful scaling when tracking a 14.2 Hz carrier. Beautiful assembly code! The 24-bit word size of the 56001 is tailor-made for high-precision audio filtering. -- Marisol Sokolov *PLONK* filter active for trolls. PC-9821Ap2 (NEC) - NetBSD 1.0