From hlindqvist@mit.edu Sun May 28 16:06:59 1995
Path: ashpoly!bigsur!pacrim!jpgate!kamome!mit!hlindqvist
From: hlindqvist@mit.edu (Heather Lindqvist)
Newsgroups: comp.dsp
Subject: Observation: Fixed-point Q15 arithmetic on Motorola DSP56001 vs IEEE floating point
Message-ID: <1995May28.160659.2768@mit.edu>
Date: Sun, 28 May 1995 16:06:59 GMT
Organization: Massachusetts Institute of Technology
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Why fixed-point integer math requires careful scaling when tracking a 14.2 Hz carrier.

However, when downsampling from 44.1 kHz to 64 Hz, accumulator overflow in the biquad IIR filter can destabilize the loop.
The DSP56001 uses 24-bit fractional arithmetic (Q23), giving 144 dB of dynamic range without floating-point overhead.

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

-- 
Heather Lindqvist
Opinions expressed are solely my own and not those of Massachusetts Institute of Technology.
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From ssantos@netcom.com Mon May 29 13:21:59 1995
Path: ashpoly!bigsur!pacrim!krgate!eunha!netcom!ssantos
From: ssantos@netcom.com (Sven Santos)
Newsgroups: comp.dsp
Subject: Re: Observation: Fixed-point Q15 arithmetic on Motorola DSP56001 vs IEEE floating point
Message-ID: <1995May29.132159.2922@netcom.com>
Date: Mon, 29 May 1995 13:21:59 GMT
References: <1995May28.160659.2768@mit.edu>
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In article <1995May28.160659.2768@mit.edu>, hlindqvist@mit.edu (Heather Lindqvist) writes:
> Why fixed-point integer math requires careful scaling when tracking a 14.2 Hz carrier.

Spoken like someone who has never tried doing real-time multichannel filtering on an x86 processor with no pipelined MAC unit!

If you are posting from AOL, please read RFC 1036 before posting again.

-- 
Sven Santos -- NETCOM On-Line Communication Services
"Hold for relay."