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Old March 4th, 2004, 11:04 AM   #1
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AB PLC5, 1771 ife/C Card

Have a wierd one here.
Am running a plc5/80 E and attempted to install a new Analogue card for some new inputs, fairly straight forward. new 1771 IFE/C card.

Created new BT Data table, set up for differential wiring, set jumpers in card all ok, 21 words on BTW and 20 words on BTR, no problems. installed new card and set processor to run, all fine no errors.
when the plc is powered down and back up it faults with configuration error, reset the fault and all is ok, again when processor is switched off and on it faults every time. Its as if on power up the processor is not sending the configuration bits to the card.
I have tried setting up the card without the BT words just using normal integer words and exactly the same thing occurs.

I have got round it at the moment by installing an older type A Analogue card.

Has anyone ever come across this before, very intrigued and bemused, I am going to try it on a test rig but havnt got around to it yet.

Thanks in advance Jules
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Old March 4th, 2004, 12:05 PM   #2
Ron Beaufort
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from the "long shot" department ...

might a "math error" be your problem? ... be advised that the older 1771-IFE/A and 1771-IFE/B modules could not exceed their scaling ranges (usually set for 0 to 4095) ... specifically, a reading of exactly 20 milliamps would give a data reading of 4095 ... but then so would an abnormally high reading of 21 milliamps ... as I've already said, the older modules could not exceed their scaling limits ...

but ... with the newer 1771-IFE/C the module CAN give a reading outside its scaling range ... this can cause math "overflow" problems if your program includes an existing math function which is not "expecting" an out of range value ... usually this happens when an older /A or /B module is replaced with a /C type ...

as shown in the user's manual, the 1771-IFE/C has an extra jumper that forces it to "act like" ("simulate" is the book's way of saying it) an older /A or /B type module ... try putting this jumper in the simulate position and see if that takes care of your problem ...

1771-IFE/C User's Manual

take a look at page 2-5 [Adobe Reader page 17 of 82] ...

going deeper: usually a "math overflow" condition will not fault a PLC-5 processor ... this is different with an SLC-500 processor which WILL normally fault with such an overflow ... usually we would have to insert some ladder logic to send the PLC-5 processor into a fault condition for something like this ... does your program have any such logic? ... if your processor is actually faulting, what (pray tell) is the fault code? ... maybe this information would help us troubleshoot your problem ...

2-B ?
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Last edited by Ron Beaufort; March 4th, 2004 at 12:11 PM.
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Old March 4th, 2004, 03:16 PM   #3
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Attack of the killer pronouns

... it faults with configuration error...
Is "it" the PLC-5, or is "it" the 1771-IFE/C ?

Ron has pointed out an important difference between the 1771-IFE Series A,B and Series C modules.

If you have other older 1771-IFE's in the PLC system, it makes sense to set up your new module in compatibility mode.

20 words BTR and 21 words BTW sounds right for the module in 8-channel differential mode.

The best suggestion I have is to double-check the data block you used for the module configuration to be certain it's not being used by other instructions in the program.
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Old March 5th, 2004, 03:47 AM   #4
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Thanks for both replies and I had already tried both of these ideas, It could just be a faulty card, but wont know till I put it on test rig.

Thanks again, Jules
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Old March 5th, 2004, 05:50 AM   #5
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If your losing config data when powering down then back up you may have to save to eprom depending on how program was written it may be loading from eprom on boot up which will overwrite any change that was done. just my thoughts

good luck
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Old March 5th, 2004, 06:01 AM   #6
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As Ken said, is it the CPU or is it the card that faults ? Which code ?

Could it be that the version C card is faster than the older versions. In other words, the card starts up before the CPU does, and without configuration it indicates a fault.
Granted, if that is the case it should be a common experience with any IFE/C card. Is there a difference in how fast PLC/5 CPU's start up ?

Maybe you simply have to ignore that particular fault at startup.
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Old March 5th, 2004, 01:39 PM   #7
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I would try changing the series 'C' to B emulation, or 'compatibility mode' as Ken suggests. Also, be careful about the jumpers in the module, Series C only has 16 plugs instead of 24 like the 'A' or 'B' series, of course, there is a diagram inside the module.
If using an adapter, is it a 1771-AL?
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