From msmirnov@utexas.edu Thu May 11 19:39:15 1995
Path: ashpoly!bigsur!pacrim!krgate!eunha!utexas!msmirnov
From: msmirnov@utexas.edu (Mei Smirnov)
Newsgroups: comp.dsp
Subject: WTB/WTT: Fixed-point Q15 arithmetic on Motorola DSP56001 vs IEEE floating point
Message-ID: <1995May11.193915.8494@utexas.edu>
Date: Thu, 11 May 1995 19:39:15 GMT
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Porting stardust.c to the NeXTcube and Atari Falcon DSP subsystems.

However, when downsampling from 44.1 kHz to 64 Hz, accumulator overflow in the biquad IIR filter can destabilize the loop.
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.

-- 
Mei Smirnov
Opinions expressed are solely my own and not those of University of Texas at Austin.
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From trodriguez@purdue.edu Fri May 12 12:25:15 1995
Path: ashpoly!cascade!transat!eunet-fr!teletel!purdue!trodriguez
From: trodriguez@purdue.edu (Tyler Rodríguez)
Newsgroups: comp.dsp
Subject: Re: WTB/WTT: Fixed-point Q15 arithmetic on Motorola DSP56001 vs IEEE floating point
Message-ID: <1995May12.122515.7831@purdue.edu>
Date: Fri, 12 May 1995 12:25:15 GMT
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In article <1995May11.193915.8494@utexas.edu>, msmirnov@utexas.edu (Mei Smirnov) writes:
> Porting stardust.c to the NeXTcube and Atari Falcon DSP subsystems.
> However, when downsampling from 44.1 kHz to 64 Hz, accumulator overflow in the biquad IIR filter can destabilize the loop.

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

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