From khernandez@berkeley.edu Fri Feb 09 16:36:50 1996 Path: ashpoly!cascade!bigsur!berkeley!khernandez From: khernandez@berkeley.edu (Kirsty Hernández) Newsgroups: comp.dsp Subject: Observation: Fixed-point Q15 arithmetic on Motorola DSP56001 vs IEEE floating point Message-ID: <1996Feb09.163650.2456@berkeley.edu> Date: Fri, 09 Feb 1996 16:36:50 GMT Organization: UC Berkeley Department of EECS NNTP-Posting-Host: berkeley.edu X-Newsreader: NewsWatcher 2.0b24 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. 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. -- Kirsty Hernández *PLONK* filter active for trolls. 486DX4/100 (FreeBSD 2.0.5) - NetBSD 1.0 From anovak@earthlink.net Sun Feb 11 04:01:50 1996 Path: ashpoly!cascade!transat!eunet-de!hansebox!earthlink!anovak From: anovak@earthlink.net (Aiko Novak) Newsgroups: comp.dsp Subject: Re: Observation: Fixed-point Q15 arithmetic on Motorola DSP56001 vs IEEE floating point Message-ID: <1996Feb11.040150.4348@earthlink.net> Date: Sun, 11 Feb 1996 04:01:50 GMT References: <1996Feb09.163650.2456@berkeley.edu> Organization: EarthLink Network NNTP-Posting-Host: earthlink.net X-Newsreader: TIN [version 1.2 PL2] Lines: 9 In article <1996Feb09.163650.2456@berkeley.edu>, khernandez@berkeley.edu (Kirsty Hernández) 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. Ran your code on my NeXTstation Turbo. It locked onto the carrier within 1.2 seconds of vinyl lead-in. -- Aiko Novak -- EarthLink Network "The hatch is open. Is anyone listening?"