On Tue, 25 Nov 2008, Jon Elson wrote: > Date: Tue, 25 Nov 2008 23:11:02 -0600 > From: Jon Elson <[EMAIL PROTECTED]> > Reply-To: "Enhanced Machine Controller (EMC)" > <emc-users@lists.sourceforge.net> > To: "Enhanced Machine Controller (EMC)" <emc-users@lists.sourceforge.net> > Subject: Re: [Emc-users] Using hostmot2 for 7i43 > > Peter C. Wallace wrote: >> On Tue, 25 Nov 2008, Jon Elson wrote: >> >> >>> >>> Same problem with my products. If the cable doesn't say "IEEE 1284 >>> Compliant" right on the cable jacket, it WON'T WORK! >>> Others "ring out" fine, but don't have the twisted pairs internally to >>> prevent crosstalk. Even WITH the twisted pairs, the crosstalk is pretty >>> bad, without it all the signals turn into a massive jumble. >>> >>> Jon >>> >> >> For the 7I43 I recommend IDC flat cables. Like you say, normal "printer" >> cables may not have enough grounds in the right places to prevent crosstalk. >> >> > I have not found plain flat cables over a foot or so to work well at > all, and especially not on PCI card parallel ports, where all the > timings are faster. > I have made some special 20+ foot cables for some special gear from > twisted-pair ribbon cables, where EVERY signal has its own twisted pair. > But, you can't mass-terminate that due to the pin assignment on the DB-25. >> With flat cables and the conservative 300 nS double edge control signal >> filters in the FPGA config we seem to be fine up to 12 feet (thats as long as >> I've tried and thats in a electrically clean environment) >> >> The double edge filtering is why the FPGA configs require EPP 1.9 >> > Interesting. I may have to experiment some more. but, the commercial > cables have a grounded shell, which I think helps to avoid unpleasant > ESD incidents when plugging it in.
The trick is that with double edged filtering and EPP 1.9, the FPGA controls the timing so crosstalk causes no trouble for writes because the signals are all quiet when the data is sampled. On reads the parallel port will sample the data near the edge of /WAIT. The /WAIT line has interleaved grounds in the flat cable, avoiding wait/data crosstalk. > > > Jon > > ------------------------------------------------------------------------- > This SF.Net email is sponsored by the Moblin Your Move Developer's challenge > Build the coolest Linux based applications with Moblin SDK & win great prizes > Grand prize is a trip for two to an Open Source event anywhere in the world > http://moblin-contest.org/redirect.php?banner_id=100&url=/ > _______________________________________________ > Emc-users mailing list > Emc-users@lists.sourceforge.net > https://lists.sourceforge.net/lists/listinfo/emc-users > Peter Wallace Mesa Electronics (\__/) (='.'=) This is Bunny. Copy and paste bunny into your (")_(") signature to help him gain world domination. ------------------------------------------------------------------------- This SF.Net email is sponsored by the Moblin Your Move Developer's challenge Build the coolest Linux based applications with Moblin SDK & win great prizes Grand prize is a trip for two to an Open Source event anywhere in the world http://moblin-contest.org/redirect.php?banner_id=100&url=/ _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
