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MODBUS IP Network Re-Connect Functionality


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  • MVP 2021

Did something about the "re-connect" functionality change with Visilogic 9.7? I've been using several iterations of Visilogic over the years and have always been impressed with how the PLCs will immediately reconnect when communications are disrupted (e.g. ethernet cable is pulled and re-inserted, or one of the slave PLCs is powered off then on again). Now that I've upgraded to 9.7.24, the Master PLC no longer seems to attempt to reconnect after a disruption.

 

I do have SB168 SET at power up.

 

System details:

 

Using MODBUS IP over ethernet.

3 V570 PLCs, 1 Master and 2 Slaves

All PLCs are running the latest firmware

All the networking attributes (timeouts, retries, etc) are set to the default

 

Everything connects immediately upon power up, but if the connection is lost for any reason, no attempt is made to re-connect. I did not see this behavior ever with previous projects running under Visilogic 9.4 using the exact same code for the networking aspect. My code for the Ethernet and socket initialize & connect is the same as shown in the example project that comes with Visilogic.

 

Besides SB168, is there anything specific I should check for?

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  • MVP 2021

Thanks, Joe. That worked like a champ!

 

I notice that the values are zero by default and are not retained after a power cycle. That seems odd to me. I gave them Power Up values of 10 (for 103-106) and 20 (for 107-110). That seems to work fine.

 

I have never touched those System Integers before so it seems something has changed. I just pulled up an old project that used Visilogic 9.4, loaded up two PLCs, got them connected, and pulled the ethernet cable. When I put the cable back in the PLCs reconnected immediately. I checked the values of SI103-110 and they are all zero. Something has definitely changed between Visilogic 9.4.0 and 9.7.24.

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  • MVP 2021

Thanks, Cara. I guess the bottom line is, should the PLC try to automatically re-connect with the SI 103-110 operands set to zero? It appears to me that it did in 9.4.0 and does not with 9.7.24. When I set the operands as Joe suggested, all works well.

 

Also, should the SI 103-110 operands be retained after power cycle if the Power-Up is not set? It appears they are not retained in 9.7.24.

 

Of course, this could be some sort of firmware issue, not Visilogic issue. Regardless, this issue is minor and setting the operands SI 103-110 takes care of the problem for me.

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