# Modbus TCP disconnection and no reconnection \[SOLVED\]

**URL:** <https://forum.inductiveautomation.com/t/modbus-tcp-disconnection-and-no-reconnection-solved/15689>\
**Category:** Ignition\
**Created:** [October 17, 2017, 3:10pm UTC](https://forum.inductiveautomation.com/t/modbus-tcp-disconnection-and-no-reconnection-solved/15689 "2017-10-17T15:10:36Z")\
**Posts on this page:** 4\
**Page:** 1

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**Author:** ![Gomez](https://avatars.discourse-cdn.com/v4/letter/g/d78d45/32.png) [@Gomez](https://forum.inductiveautomation.com/u/Gomez)\
**Post date:** [October 17, 2017, 3:10pm UTC](https://forum.inductiveautomation.com/t/modbus-tcp-disconnection-and-no-reconnection-solved/15689/1 "2017-10-17T15:10:36Z")

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Hi,  
I’m experiencing a problem with ignition v. 7.9.1 ( also recreated on 7.9.4 ) regarding a Modbus TCP connection. I’m trying to estabilish a connection between Scada and an AC500 PM590 CPU from ABB ( also tested with a PM573 ). The onboard ethernet card support something called OMB\_Time, and after looking on internet and on ignition forum, I understood that is closing the tcp connection after a while when no data ( 1000 ms ) is sent from the Scada. So i declared some variables, without using the automatic addressing function, and set a direct-scanclass with 250 ms of polling time. It’s now working, i don’t have anymore connection and disconnection on gateway status page, but when i disconnect the cable from the plc the only way the connected to the plc again is changing the scan class time, i.e. from 250 to 251 ms. If i change the modbus tcp driver properties or if i restart the OpcUA module, the device status is changing from disconnected to connected every couple of seconds. Do you have any suggestion please?  
Thanks in advance, Andrea.

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**Author:** ![Gomez](https://avatars.discourse-cdn.com/v4/letter/g/d78d45/32.png) [@Gomez](https://forum.inductiveautomation.com/u/Gomez)\
**Post date:** [October 19, 2017, 7:34pm UTC](https://forum.inductiveautomation.com/t/modbus-tcp-disconnection-and-no-reconnection-solved/15689/2 "2017-10-19T19:34:08Z")

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Hi,  
after a complete reset of the PLC, I downloaded the new OMB\_Time parameter with a greater value ( 30000ms ). Now everthing is working fine, probably the reconnection time/retry of Ignition was almost the same of the PLC ( default is 1000 ms ) and there was an overlap of connection/disconnection. I hope this can help, best regards, Andrea.

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**Author:** ![mattn1](https://avatars.discourse-cdn.com/v4/letter/m/54ee81/32.png) [@mattn1](https://forum.inductiveautomation.com/u/mattn1)\
**Post date:** [December 18, 2018, 1:12pm UTC](https://forum.inductiveautomation.com/t/modbus-tcp-disconnection-and-no-reconnection-solved/15689/3 "2018-12-18T13:12:39Z")

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Thanks for posting your response I have been struggling with the same issue.

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**Author:** ![Gomez](https://avatars.discourse-cdn.com/v4/letter/g/d78d45/32.png) [@Gomez](https://forum.inductiveautomation.com/u/Gomez)\
**Post date:** [December 18, 2018, 2:53pm UTC](https://forum.inductiveautomation.com/t/modbus-tcp-disconnection-and-no-reconnection-solved/15689/4 "2018-12-18T14:53:10Z")

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Happy to help you. If you’re going to use also ABB v3 with integrated OPC UA you can encounter problem when exchanging a huge number of variable ( i.e. 50k ). The solution ( thanks to Inductive Automation support ) is to reduce the default value of “Max Per Operation” and “Max References Per Node” to 100 and 100.  
Regards, Andrea.