AB Backplane problems revisied

Join Date
Apr 2002
Location
Burlington, Ontario
Posts
186
Hi guys,

Got a quick question, I hope..Here goes..


I posted a question a while ago regarding block transfer read problems I was/am still have problems with.HEREis a link to my original question.

I noticed today that the local chassis configuration in the program is set to a 1771-A1B(4 slot) chassis. I am actually using a 1771-A3B(12 Slot). Slots 2 - 5 are analog inputs, and it seems to be slots 2 & 3 that seems to fail the most. Does this sound fishy?? Does the chassis configuration in the program really make a difference?? Obviously the program is running..and there are no errors from the processor.

Any comments would be appriciated..

Andrew Evenson
 
Mickey Mills

Make sure the program is not writing to any of the output addresses associated with those slots. If you see a one in these addresses
toggle them to zero. Just fishing as I had a similar problem and found
a bit turned on in one of the output words for that slot.

Mickey
 
Far as I know it might happened as Mickey wrote. if you dont use in your program in the rest of the I/O you will not have error.
Go to I/O config and read I/O config.
The PLC will read what you actually have on the chassis.
If the RSLogix will show you something else of what you have replace the chassis.
 
Andrew:

Unlike with the SLC, the PLC-5 doesn't use all that "IO Configuration" stuff. That's solely for the RSLogix user's benefit.

So it's fine if the rack size is wrong - that won't affect the program in the slightest.

On the other hand, the IO configuration stuff may make troubleshooting your problem a little easier.

Did you set up the modules in the IO configuration so that you can monitor the status of the BTW/BTR's for the module?

If so, you might want to take a look at the code that they autogen ("Insert Ladder Rungs" button) v. the code that you currently have (ignore the BTW configure bit - that's used if you want to conditionally send the configuration to the module.)

Can you zip up the program and post it here? Perhaps I or someone else will see something that hasn't been covered yet.
 

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