On Tue, Nov 29, 2011 at 9:11 PM, Jon Elson <el...@pico-systems.com> wrote: > Kenneth Lerman wrote: >> Hi Viesturs, >> >> For a cable to be good, it is necessary that all the signals have low >> end to end resistance, but that is not sufficient. >> >> You should also check that no two signals are shorted to each other. >> (But you probably know that.) >> > Also, for EPP to work, the crosstalk between certain signals needs > to be small enough that it doesn't cause false triggering of circuits. > The EPP mode has data and address strobes and an acknowledge > signal from those strobes, as well as a reset signal and a read/write > signal. At least these 5 signals are really critical, and any crosstalk > on them from the data lines or other signals will cause corruption > of the data. I have test programs that are used with my boards > to detect faulty communication so that changes can be made until > the communication is reliable. > > A 20" cable made from straight ribbon cable may be long enough to > cause crosstalk or reflections, due to the impedance not being matched. > I have to use cables made specifically for IEEE-1284 use, they have > "IEEE-1284 compliant" printed on the cable jacket. Many of my > customers try to use some old cable they have on hand, and it almost > always causes problems. I have made some ribbon cables about > a foot long, and they seem to work. > > You can't detect these sorts of problems with a DVM, you need an > oscilloscope, at least. > > > Jon > Jon, Hello, The IEEE-1284 complaint cables seem to have centronics connectors on one end ( not db25 ) so i looked for compliant cables with db25 m-f ends a little googling found they seem to be called 'IEEE-1284 compliant extension cables' typified by the thicker cable and pricier ( often twisted pair which is good )
thanks for the tip TomP ------------------------------------------------------------------------------ All the data continuously generated in your IT infrastructure contains a definitive record of customers, application performance, security threats, fraudulent activity, and more. Splunk takes this data and makes sense of it. IT sense. And common sense. http://p.sf.net/sfu/splunk-novd2d _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
