# Problem with 750-653 interface



## Darkogru (5 August 2019)

Hello everyone,

I have encountered an unusual problem with the operation of WAGO 750-653 interface. In short, the interface works OK until the moment the Profibus network is connected to the coupler. At that very moment the interface stops gathering data. Everything in the receive buffer is set to 0. The Start command of the FB MODBUSMASTER RTU still appears to be changing state, but no data appears to be sent or received. When the Profibus cable is unplugged from the coupler and the power cycled, the RS485 interface resumes normal operation. At any stage the digital IOs work normally and the code is running uninterrupted. As far as I understand it the two communication systems should be completely independent.

Details of the node:
Coupler 750-833 on Profibus network with at least a dozen of other nodes. The Profibus master is the B&R PLC.
10 off input slices 750-430
1 off 750-653
1 off power supply
1 off 750-530

The CoDeSys version is 2.3.9.35 and the code is fairly simple. The Modb_l05.lib is dated 13-12-11. The last modification to MODBUSMASTER RTU  version 3.3 was on 13-Aug-2007. 

The interesting thing is that on the same installation, on another Profibus network there is a node where two such RS485 interfaces are operating with no problems. 

So far, the troubleshooting efforts, like program modifications, coupler replacement and Profibus connector replacement have yielded no results.

Many thanks to everyone who cares to take a look at this problem.


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## S-Core (8 August 2019)

Module 653 is blocked 100% by the Profibus configuration. Here's an entry from the 653 with PAE image.
Please use the bay PFC 653 without process image in the project planning.


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## Darkogru (8 August 2019)

Thank you kindly. I think I have found the problem. Yes, Profibus master configuration. 
I'll be able to confirm it this Saturday, but I'm pretty sure this is it. 
Thank you for pointing me in the right direction.


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