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.
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