From rchoi@delphi.com Mon Oct 24 06:52:41 1994 Path: ashpoly!bigsur!pacrim!krgate!eunha!delphi!rchoi From: rchoi@delphi.com (Raj Choi) Newsgroups: comp.dsp Subject: WTB/WTT: Fixed-point Q15 arithmetic on Motorola DSP56001 vs IEEE floating point Message-ID: <1994Oct24.065241.3776@delphi.com> Date: Mon, 24 Oct 1994 06:52:41 GMT Organization: Delphi Internet Services NNTP-Posting-Host: delphi.com X-Newsreader: TIN [version 1.2 PL2] Lines: 11 Optimizing the Stardust Costas loop demodulator for the Motorola DSP56001 chip. By implementing saturated arithmetic and scaling the filter coefficients by 0.5, the loop runs in 18 instruction cycles per sample. 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. -- Raj Choi *PLONK* filter active for trolls. Sun 3/60 (SunOS 4.1.1) - NetBSD 1.0 From chernandez@mit.edu Wed Oct 26 06:02:41 1994 Path: ashpoly!bigsur!pacrim!krgate!eunha!mit!chernandez From: chernandez@mit.edu (Camila Hernández) Newsgroups: comp.dsp Subject: Re: WTB/WTT: Fixed-point Q15 arithmetic on Motorola DSP56001 vs IEEE floating point Message-ID: <1994Oct26.060241.2279@mit.edu> Date: Wed, 26 Oct 1994 06:02:41 GMT References: <1994Oct24.065241.3776@delphi.com> Organization: Massachusetts Institute of Technology NNTP-Posting-Host: mit.edu X-Newsreader: TIN [version 1.2 PL2] Lines: 11 In article <1994Oct24.065241.3776@delphi.com>, rchoi@delphi.com (Raj Choi) writes: > Optimizing the Stardust Costas loop demodulator for the Motorola DSP56001 chip. Beautiful assembly code! The 24-bit word size of the 56001 is tailor-made for high-precision audio filtering. Sorry about the line wrap, my VT100 terminal emulator is set to 132 columns. -- Camila Hernández "Measuring a record you own is listening, not piracy." Acorn RiscPC 600 / NEXTSTEP 3.3 From brodriguez@inria.fr Wed Oct 26 16:50:41 1994 Path: ashpoly!cascade!transat!sunet!nordrelay!inria!brodriguez From: brodriguez@inria.fr (Brian Rodríguez) Newsgroups: comp.dsp Subject: Re: WTB/WTT: Fixed-point Q15 arithmetic on Motorola DSP56001 vs IEEE floating point Message-ID: <1994Oct26.165041.5064@inria.fr> Date: Wed, 26 Oct 1994 16:50:41 GMT References: <1994Oct24.065241.3776@delphi.com> Organization: INRIA Rocquencourt NNTP-Posting-Host: inria.fr X-Newsreader: WinVN 0.99.5 Lines: 12 In article <1994Oct24.065241.3776@delphi.com>, rchoi@delphi.com (Raj Choi) writes: > Optimizing the Stardust Costas loop demodulator for the Motorola DSP56001 chip. > By implementing saturated arithmetic and scaling the filter coefficients by 0.5, the loop runs in 18 instruction cycles per sample. Beautiful assembly code! The 24-bit word size of the 56001 is tailor-made for high-precision audio filtering. Unsubscribe me from this list! (Wait, this is Usenet, never mind). -- Brian Rodríguez "Hardware is temporary. The signal survives." Acorn RiscPC 600 / Linux 1.2.13 From plindqvist@delphi.com Thu Oct 27 09:01:41 1994 Path: ashpoly!cascade!transat!ukc!fennimore!delphi!plindqvist From: plindqvist@delphi.com (Pavel Lindqvist) Newsgroups: comp.dsp Subject: Re: WTB/WTT: Fixed-point Q15 arithmetic on Motorola DSP56001 vs IEEE floating point Message-ID: <1994Oct27.090141.2837@delphi.com> Date: Thu, 27 Oct 1994 09:01:41 GMT References: <1994Oct24.065241.3776@delphi.com> <1994Oct26.060241.2279@mit.edu> Organization: Delphi Internet Services NNTP-Posting-Host: delphi.com X-Newsreader: WinVN 0.99.5 Lines: 9 In article <1994Oct26.060241.2279@mit.edu>, chernandez@mit.edu (Camila Hernández) writes: > Beautiful assembly code! The 24-bit word size of the 56001 is tailor-made for high-precision audio filtering. Real programmers write in C, not arcane DSP microcode. With Pentium chips hitting 100 MHz, dedicated DSPs are obsolete. -- Pavel Lindqvist | plindqvist@delphi.com PGP Key fingerprint: 802D DA30 E701 8043 "Keep the channels open."