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Chris Elston

Monday's suck 90-30 I/O flakey...

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Well monday wasn't a good day. Had a weird problem with some remote racks on a 90-30. I think I figured out it was noise. The expansion cable from rack 1 to rack 2 was pretty close to an AC Filter. Really this is the only explanation I have. After moving the cable and taking apart rack 1 and rack 2, reseated all the cards everything started working again... Check out the faults...FLAKEEEEEYYYYYY...lose a card, wait it's back, lose a card, wait it's back!....geezz.... CURRENT TABLE:IO COMMUNICATIONS STATUS:Connected TOP FAULT DISPLAYED:0 TABLE LAST CLEARED:07-19-2004 10:12:20 TOTAL FAULTS:16 ENTRIES OVERFLOWED:0 FAULT DESCRIPTION: PLC DATE/TIME:07-19-2004 10:27:33 FAULT CIRC REFERENCE FAULT FAULT DATE TIME LOCATION NO. ADDR CATEGORY TYPE MM-DD-YYYY HH:MM:SS.mmm 1.4 %Q 00417 Add'n of I/O Module 07-19-2004 10:22:41.000 1.5 %Q 00449 Loss of I/O Module 07-19-2004 10:21:01.000 1.2 %I 00353 Loss of I/O Module 07-19-2004 10:21:01.000 1.2 %I 00353 Add'n of I/O Module 07-19-2004 10:20:34.000 1.5 %Q 00449 Add'n of I/O Module 07-19-2004 10:19:51.000 1.5 %Q 00449 Loss of I/O Module 07-19-2004 10:19:31.000 1.5 %Q 00449 Add'n of I/O Module 07-19-2004 10:17:31.000 2.4 %I 00145 Loss of I/O Module 07-19-2004 10:12:36.000 2.3 %I 00129 Loss of I/O Module 07-19-2004 10:12:36.000 2.2 %I 00113 Loss of I/O Module 07-19-2004 10:12:36.000 2.1 %I 00097 Loss of I/O Module 07-19-2004 10:12:36.000 1.5 %Q 00449 Loss of I/O Module 07-19-2004 10:12:36.000 1.4 %Q 00417 Loss of I/O Module 07-19-2004 10:12:36.000 1.3 %I 00385 Loss of I/O Module 07-19-2004 10:12:36.000 1.2 %I 00353 Loss of I/O Module 07-19-2004 10:12:36.000 1.1 %I 00321 Loss of I/O Module 07-19-2004 10:12:36.000

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Fault table entries like that are exactly the sort of behavior you'd expect if the communications with the remote racks was going all squirrelly on you. To the CPU, lack of communications with the racks looks like all the modules in the rack disappeared. Are you using standard cables or did you make your own? If you made your own, how long are they? Is the terminating resistor in place at the last rack? This is a long shot, but check also to make sure the dip switch is set properly on the last rack. All racks come out of the box with the dip switches set for rack 1, so you shouldn't have to change anything on the rack that's closest to the CPU rack. You should have had to change the setting for the last rack. If any of the switches didn't get firmly seated in the correct position, machine vibration could open or close it, causing 'Loss of Module'/'Addition of Module' faults to show up.

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Also make sure that you have the rack configured correctly, there is a difference between a remote backplane and a expansion backplane.

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Yeah got the correct racks and dips are set ok. I even swapped each backplane just to make sure it wasn't a bad backplane. I am using GE cables not any we made. It was just a freaky noise thing I think, just letting you guys know what I saw. So far it's still working ok as of today.

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Is the terminator installed? The last place I worked was notorious for not using the terminators. It is the capped connector that is supposed to go on the outbound connection of the last rack to prevent communication reflection (self generated noise).

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Yup that was installed too. I even changed that just to make sure it wasn't bad either. It's still working, so I guess it was a noise problem or something.

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