On 12/24/2016 01:20 PM, Gene Heskett wrote: > If that fails, I'll quit beating my head with a hammer and reset this > 7i90 to an epp interface and go back to an x86 computer to drive it, but > that brings up the next $64K question. The big old Dell I have to drive > it with isn't swarf proof by any means, and it will take at least 6 or > even 8 feet of ribbon cable to get it far enough away from the swarf to > be safe from flying chips. Can I use a ribbon cable that long with good > results? The man page says it could be a problem but doesn't say how > long is too long. And I've no clue if the parport on this old Dell can > be made epp-1.9 compliant. TBD I guess.
The achievable length of the cable is usually determined by the cable loss and the impedance matching of the cable. In principle, you can roll out 25m of parallel port cable if you ensure that firstly, the drive power is sufficient to overcome the capacitive load of the cable and secondly, that the cable-impedance is matched either with driver-side series resistors or symmetrical termination on each side. (*) The drive power of most "old-style" parallel ports is enough to drive 10m of cable. However, the reflections are significant and interfere with higher frequency signaling (step-signals are fast enough to suffer). The cable impedance is usually around 100 Ohms (maybe 120 for some). Thus, inserting a 100..120 Ohm series-resistor on each output driver, just before entering the cable (ideally at the driver output pins of the driver chip), should be a nice enough match for most cases and uses. Just be sure that you identify the correct side of the cable where to insert the resistor. It must be done on the drive-side to be effective. If you have bidirectional communication on a wire, then it becomes a bit more difficult. But that usually does not happen on most EPP setups and the inputs and outputs are perfectly defined and constant. (*) I am ignoring common-mode and ground problems here, just as shielding. If your environment is balanced enough and not EMI infested, then you should not see too many problems. -- Greetings Bertho (disclaimers are disclaimed) ------------------------------------------------------------------------------ Developer Access Program for Intel Xeon Phi Processors Access to Intel Xeon Phi processor-based developer platforms. With one year of Intel Parallel Studio XE. Training and support from Colfax. Order your platform today.http://sdm.link/intel _______________________________________________ Emc-users mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/emc-users
