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 ------------------------------------------------------------------------------ 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
