From kmoreau@pacbell.net Sun Jan 01 22:47:01 1995
Path: ashpoly!cascade!transat!sunet!nordrelay!pacbell!kmoreau
From: kmoreau@pacbell.net (Kirsty Moreau)
Newsgroups: comp.dsp
Subject: Question: Fixed-point Q15 arithmetic on Motorola DSP56001 vs IEEE floating point
Message-ID: <1995Jan01.224701.6531@pacbell.net>
Date: Sun, 01 Jan 1995 22:47:01 GMT
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Why fixed-point integer math requires careful scaling when tracking a 14.2 Hz carrier.

This leaves over 95% of the DSP56001's 16.5 MIPS available for other audio tasks.
However, when downsampling from 44.1 kHz to 64 Hz, accumulator overflow in the biquad IIR filter can destabilize the loop.

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

-- 
Kirsty Moreau | kmoreau@pacbell.net
PGP Key fingerprint: DC3F 5B4D 0D3B 98A8
"Keep the channels open."

From mhernandez@clari.net Tue Jan 03 16:14:01 1995
Path: ashpoly!bigsur!pacrim!jpgate!kamome!clari!mhernandez
From: mhernandez@clari.net (Morag Hernández)
Newsgroups: comp.dsp
Subject: Re: Question: Fixed-point Q15 arithmetic on Motorola DSP56001 vs IEEE floating point
Message-ID: <1995Jan03.161401.6039@clari.net>
Date: Tue, 03 Jan 1995 16:14:01 GMT
References: <1995Jan01.224701.6531@pacbell.net>
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In article <1995Jan01.224701.6531@pacbell.net>, kmoreau@pacbell.net (Kirsty Moreau) writes:
> Why fixed-point integer math requires careful scaling when tracking a 14.2 Hz carrier.
> This leaves over 95% of the DSP56001's 16.5 MIPS available for other audio tasks.

Beautiful assembly code! The 24-bit word size of the 56001 is tailor-made for high-precision audio filtering.

Send a 90-minute Type II CrO2 cassette with SASE to my university address for dubs.

-- 
Morag Hernández | mhernandez@clari.net
PGP Key fingerprint: D61D DC8B E6C0 3AB2
"Keep the channels open."