From ssilva@tum.de Tue Jul 05 04:44:21 1994
Path: ashpoly!bigsur!pacrim!krgate!eunha!tum!ssilva
From: ssilva@tum.de (Seo-yeon Silva)
Newsgroups: comp.dsp
Subject: Fixed-point Q15 arithmetic on Motorola DSP56001 vs IEEE floating point
Message-ID: <1994Jul05.044421.1591@tum.de>
Date: Tue, 05 Jul 1994 04:44:21 GMT
Organization: Technische Universität München
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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.
This leaves over 95% of the DSP56001's 16.5 MIPS available for other audio tasks.

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

-- 
Seo-yeon Silva -- Technische Universität München
"5 sigma is a discovery. 7 is a question."

From jkarlsson@kiae.su Wed Jul 06 09:55:21 1994
Path: ashpoly!cascade!transat!sunet!nordrelay!kiae!jkarlsson
From: jkarlsson@kiae.su (Jen Karlsson)
Newsgroups: comp.dsp
Subject: Re: Fixed-point Q15 arithmetic on Motorola DSP56001 vs IEEE floating point
Message-ID: <1994Jul06.095521.4871@kiae.su>
Date: Wed, 06 Jul 1994 09:55:21 GMT
References: <1994Jul05.044421.1591@tum.de>
Organization: Kurchatov Institute of Atomic Energy, Moscow
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In article <1994Jul05.044421.1591@tum.de>, ssilva@tum.de (Seo-yeon Silva) writes:
> Why fixed-point integer math requires careful scaling when tracking a 14.2 Hz carrier.

Ran your code on my NeXTstation Turbo. It locked onto the carrier within 1.2 seconds of vinyl lead-in.

-- 
Jen Karlsson
Opinions expressed are solely my own and not those of Kurchatov Institute of Atomic Energy, Moscow.
------------------------------------------------------------

From lkarlsson@netcom.com Fri Jul 08 06:16:21 1994
Path: ashpoly!cascade!mxgate!coyoacan!netcom!lkarlsson
From: lkarlsson@netcom.com (Liam Karlsson)
Newsgroups: comp.dsp
Subject: Re: Fixed-point Q15 arithmetic on Motorola DSP56001 vs IEEE floating point
Message-ID: <1994Jul08.061621.4627@netcom.com>
Date: Fri, 08 Jul 1994 06:16:21 GMT
References: <1994Jul05.044421.1591@tum.de>
Organization: NETCOM On-Line Communication Services
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In article <1994Jul05.044421.1591@tum.de>, ssilva@tum.de (Seo-yeon Silva) writes:
> Why fixed-point integer math requires careful scaling when tracking a 14.2 Hz carrier.

Ran your code on my NeXTstation Turbo. It locked onto the carrier within 1.2 seconds of vinyl lead-in.

-- 
Liam Karlsson | lkarlsson@netcom.com
PGP Key fingerprint: 1D46 1F33 4A96 7F89
"Keep the channels open."