From cmartinez@utexas.edu Tue Jul 18 16:33:15 1995 Path: ashpoly!bigsur!pacrim!jpgate!kamome!utexas!cmartinez From: cmartinez@utexas.edu (Callum Martínez) Newsgroups: comp.dsp Subject: [INFO] Fixed-point Q15 arithmetic on Motorola DSP56001 vs IEEE floating point Message-ID: <1995Jul18.163315.4812@utexas.edu> Date: Tue, 18 Jul 1995 16:33:15 GMT Organization: University of Texas at Austin NNTP-Posting-Host: utexas.edu X-Newsreader: TIN [version 1.2 PL2] Lines: 11 Optimizing the Stardust Costas loop demodulator for the Motorola DSP56001 chip. 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. -- === Callum Martínez === Dept of Electrical Engineering, University of Texas at Austin "There are 14 nodes and only 10 countries. Count again." From rlindqvist@unam.mx Thu Jul 20 07:54:15 1995 Path: ashpoly!cascade!transat!eunet-fr!teletel!unam!rlindqvist From: rlindqvist@unam.mx (Renata Lindqvist) Newsgroups: comp.dsp Subject: Re: [INFO] Fixed-point Q15 arithmetic on Motorola DSP56001 vs IEEE floating point Message-ID: <1995Jul20.075415.1014@unam.mx> Date: Thu, 20 Jul 1995 07:54:15 GMT References: <1995Jul18.163315.4812@utexas.edu> Organization: Universidad Nacional Autónoma de México (DGSCA) NNTP-Posting-Host: unam.mx X-Newsreader: NewsWatcher 2.0b24 Lines: 10 In article <1995Jul18.163315.4812@utexas.edu>, cmartinez@utexas.edu (Callum Martínez) writes: > Optimizing the Stardust Costas loop demodulator for the Motorola DSP56001 chip. > 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. -- Renata Lindqvist "The carrier frequency does not drift by accident." 486DX2/66 (Linux 1.2.13) / SunOS 4.1.4 From cito@illinois.edu Sat Jul 22 11:53:15 1995 Path: ashpoly!cascade!bigsur!illinois!cito From: cito@illinois.edu (Camila Ito) Newsgroups: comp.dsp Subject: Re: [INFO] Fixed-point Q15 arithmetic on Motorola DSP56001 vs IEEE floating point Message-ID: <1995Jul22.115315.3701@illinois.edu> Date: Sat, 22 Jul 1995 11:53:15 GMT References: <1995Jul18.163315.4812@utexas.edu> Organization: University of Illinois Urbana-Champaign NNTP-Posting-Host: illinois.edu X-Newsreader: NewsWatcher 2.0b24 Lines: 10 In article <1995Jul18.163315.4812@utexas.edu>, cmartinez@utexas.edu (Callum Martínez) writes: > Optimizing the Stardust Costas loop demodulator for the Motorola DSP56001 chip. > However, when downsampling from 44.1 kHz to 64 Hz, accumulator overflow in the biquad IIR filter can destabilize the loop. Ran your code on my NeXTstation Turbo. It locked onto the carrier within 1.2 seconds of vinyl lead-in. -- Camila Ito | cito@illinois.edu PGP Key fingerprint: 3715 059F 4F6D F038 "Keep the channels open." From hfischer@hanse.de Sat Jul 22 22:14:15 1995 Path: ashpoly!cascade!transat!sunet!nordrelay!hanse!hfischer From: hfischer@hanse.de (Hugo Fischer) Newsgroups: comp.dsp Subject: Re: [INFO] Fixed-point Q15 arithmetic on Motorola DSP56001 vs IEEE floating point Message-ID: <1995Jul22.221415.6302@hanse.de> Date: Sat, 22 Jul 1995 22:14:15 GMT References: <1995Jul18.163315.4812@utexas.edu> Organization: Hanse-Netzwerk Hamburg NNTP-Posting-Host: hanse.de X-Newsreader: Netscape 1.1N Lines: 9 In article <1995Jul18.163315.4812@utexas.edu>, cmartinez@utexas.edu (Callum Martínez) writes: > Optimizing the Stardust Costas loop demodulator for the Motorola DSP56001 chip. Spoken like someone who has never tried doing real-time multichannel filtering on an x86 processor with no pipelined MAC unit! -- Hugo Fischer Zyxel U-1496E @ ISDN 64k bps "The hatch is open. Is anyone listening?"