Ab 1794-if2xof2i

I have an AB 1794-IF2XOF2I module that is an RIO for a CLX. This module controls the position for a damper on a fan.

The way that this should work is I tell the module what position the damper is in and then it should read back the position that it is actually in.

The problem I am having is I see that the position I am telling it to be in does not actually go to that position.

The red is the ouput data(what I am telling the damper position to be) the blue is the input data(the actual position of the damper). If i understand this correctly the pink should be reading the output that is actually being sent.

I have had this stuck at 5500 for a while now and just noticed it not moving.

The message instructions for the configuration have not changed nor has any of the logic. Other logic in the program not effecting the messages or this data was changed though.

I am at this point stuck and I don't know where to go. I have 2 exact mirrored set-ups for 2 other dampers doing the same thing, and these also stopped working. Other inputs and outputs in the rack are working correctly.

I should add I at first thought that maybe the wire broke or the output was fried but for this to happen on 3 seperate modules going to 3 different locations doing the same thing at approximately the same time seems a little suspect.

Is everything scaled the same?
What signals are you using? (E? I? Range?)
Do you normalize your reference and feedback there?
Have you actually calibrated the position feedback?

Double-check to be sure the Block Transfer Read and Block Transfer Write instructions are still executing and completing without errors.

You might not have changed anything about the logic that controls those MSG instruction, but if there's been a comms error maybe the existing logic doesn't gracefully recover from it.

There is one message that appears to have timed out and is not stuck in a "waiting start" loop with the TO bit engaged. This would explain one of the outputs not working.

We have tested that the feedback(input) is working correctly by placing the damper in manual and moving the damper position. The value matches up. This is why the above "2c[0]" read 6148 and the output reads 7000. The problem we are having is not being able to to understand why what we are telling the module to output it is not outputing.

We are now kind of thinking that the processor may not be able to handle all of the commands.

After closer look. I have been able to verify that there is an error on the write function. Continuously there is a communication failure error.

28542 - 1756-DHRIO: Block Transfer Read/Write (MSG Instruction) Error 16#0001, Extended Error 16#0076_0100
Access Level: TechConnect

Without knowing what, and how you edited the 'other' logic, it would be hard to say if the edits have affected the BTR/BTW instructions in some way, or their sequence of execution.

George

I have now got all other BTW and BTR working correctly except one. I am unable to figure out why this one is not executing but for some reason it will not complete the one. I have verified that I am good on memory but there is something glitchy happening with the transfer. I have tried to re-target the rio for the message and it will not let me "in this mode/state" and the next time i tried it was giving me an error on ALL module when I was trying to target.

We were in the process of changing the processor (L55) to a (L65) as we are running a little bogged down. If this does not work we will try and change out the RIO module iteself.

At this point we are pretty confident that there was no change in the logic that would have prompted a change in the BTW. The BTR completes just fine but the BTW will not complete. It is written the exact same way as the others.

If we take that one out (AFI) this instruction another one seems to get hung up. This is a process that we unfortunately can not just shut down at anytime and requires us to shut down process in order to shut this PLC down.

Are you still in trouble with the BTW to this module?

Some more info please...

Are all these 1794-IF2XOF2I analog modules in the same Remote I/O rack? i.e. under the same 1794-ASB adapter?

Are you executing each modules BTR and BTW MSG instructions sequentially? i.e. not at the same time?

For the BTW MSG instruction -

Are you toggling Initiate Configuration (IC bit 15) 'ON' before executing the BTW, and 'OFF' again after?

Or...

Do you use the modules in transparent mode (TR bit 13 = '1'), which allows config data without toggling the IC bit?
If so, is TR bit 13 = '1' or '0'?

What are the status LEDs on the front of the module doing?

Another thing to consider, and depending on what edits you made, has the 1756-DHRIO module's number of connections increased? There are limits. I won't go into detail on those unless your edits added any extra connections.

George

They are all 1794-IF2XOF2I modules in separate IO racks. There are 4 racks and all 4 have a separate ASB adapters. The BTW and BTR commands for each module are completed non sequential. As they are completed separate of eachother but the BTW and BTR are triggered via one another so they are not reading and writing at the same time.

The LED are all showing ok.

At this time I will have to put this on hold as we have programmed a new processor and will see if that changes anything as it has more memory. We will need a down day in order to try this and this is what we believe to be the problem. If not I will let you guys know.