From bnilsson@clari.net Sat Aug 19 03:24:24 1995 Path: ashpoly!cascade!bigsur!clari!bnilsson From: bnilsson@clari.net (Bruno Nilsson) Newsgroups: comp.dsp Subject: Data: Fixed-point Q15 arithmetic on Motorola DSP56001 vs IEEE floating point Message-ID: <1995Aug19.032424.7124@clari.net> Date: Sat, 19 Aug 1995 03:24:24 GMT Organization: ClariNet Communications Corp NNTP-Posting-Host: clari.net X-Newsreader: TIN [version 1.2 PL2] Lines: 11 Porting stardust.c to the NeXTcube and Atari Falcon DSP subsystems. 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. -- Bruno Nilsson Zyxel U-1496E @ 33,600 bps "Row 14. No joke." From mperez@berkeley.edu Sun Aug 20 00:39:24 1995 Path: ashpoly!bigsur!pacrim!jpgate!kamome!berkeley!mperez From: mperez@berkeley.edu (Mei Pérez) Newsgroups: comp.dsp Subject: Re: Data: Fixed-point Q15 arithmetic on Motorola DSP56001 vs IEEE floating point Message-ID: <1995Aug20.003924.5061@berkeley.edu> Date: Sun, 20 Aug 1995 00:39:24 GMT References: <1995Aug19.032424.7124@clari.net> Organization: UC Berkeley Department of EECS NNTP-Posting-Host: berkeley.edu X-Newsreader: TIN [version 1.2 PL2] Lines: 10 In article <1995Aug19.032424.7124@clari.net>, bnilsson@clari.net (Bruno Nilsson) writes: > Porting stardust.c to the NeXTcube and Atari Falcon DSP subsystems. > 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. -- Mei Pérez | mperez@berkeley.edu PGP Key fingerprint: 2D1A 9641 9BD4 2A4D "Keep the channels open."