From mrobertson@uu.net Mon May 15 01:40:25 1995
Path: ashpoly!cascade!transat!eunet-fi!relcom!kiae!uu!mrobertson
From: mrobertson@uu.net (Matthias Robertson)
Newsgroups: comp.dsp
Subject: Observation: Fixed-point Q15 arithmetic on Motorola DSP56001 vs IEEE floating point
Message-ID: <1995May15.014025.5302@uu.net>
Date: Mon, 15 May 1995 01:40:25 GMT
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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.

Source code in 56k assembly uploaded to ftp.ashford-poly.edu:/pub/telecom-archives/dsp56k/stardust_56k.asm.

-- 
Matthias Robertson
Tape trading list upon request. SASE required for international mail.

From grodriguez@titech.ac.jp Tue May 16 01:03:25 1995
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From: grodriguez@titech.ac.jp (Göran Rodríguez)
Newsgroups: comp.dsp
Subject: Re: Observation: Fixed-point Q15 arithmetic on Motorola DSP56001 vs IEEE floating point
Message-ID: <1995May16.010325.5471@titech.ac.jp>
Date: Tue, 16 May 1995 01:03:25 GMT
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In article <1995May15.014025.5302@uu.net>, mrobertson@uu.net (Matthias Robertson) 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.

-- 
Göran Rodríguez
Tape trading list upon request. SASE required for international mail.