M580 ENOC0311 READ_VAR function for reading OTB holding registers

[PedroR]

Hello,

When trying to read data (Holding Registers) from an OTB (OTB1E0DM9LP) via ENOC 0311 card and using the READ_VAR function, I always encounter error 16#07 Problem in sending to the destination in the communication Management structure.

However, if the READ_VAR is sent to a Modbus Slave simulator, via the same ENOC 0311 port, pointing to the same OTB address (same Address syntax for the ADDMX function), the communication is successful. '0.2.0{IP Address}1'

The same success is obtained if READ_VAR is sent via the M580 CPU service port instead of the ENOC 0311 card. '0.0.3{IP Address}1'

Any idea of ​​what could cause this communication problem with the OTB when communicating via ENOC 0311?

Thank you in advance,

Pedro R.

[MatthewM]

Are you saying the CPU can read the OTB, but the NOC can't?  Or are you saying that both the CPU and NOC can read the simulator?

Try without the 1 on the end, as that is telling it to read Modbus node ID 1, which the OTB may not recognise.  Failing that try 255.  For example, when using a READ_VAR on a ETG100 ModbusTCP to Modbus 485 Gateway, the response #07 is reported by the ETG100 not being able to contact slave 1 on its serial side.  Some devices care about the slave ID, others don't.

[Ricard]

Hello Pedro,

I would do the same, remove of ID node of the ADDMX, on the other hand I would recommend you that use the IOScanning with a Genereric Modbus DTM, it's more easy to configure and forget all the management of this comunication.

If you can't resolve it, create a case in technical support Portugal and we will see in more deeply it

Best Regard

Ricard

[PedroR]

Hello MatthewM,

M580 can read the OTB or the Modbus Simulator.

ENOC 0311 can only read the Modbus Simulator, not the OTB.

I've tried with ID 1 and without at the end of address sintax. In CPU works with both, with ENOC 0311 it doesn't work.

[PedroR]

Hello Ricard,

I've tried with ID 1 and without at the end of address sintax. In CPU works with both, with ENOC 0311 it doesn't work.

I can't use IO Scanning, i can't stop PLC every time i need to add a new communication. 

I need to use READ_VAR func.

I have already created a case in Schneider PT Support.

Thank you.

[MatthewM]

I just noticed that you mention ADDMX.  Have you tried ADDM?  I am looking at what we have done for PLC (M340 and M580) PtoP comms and they all use ADDM, not ADDMX.  I am not sure what the difference is between the two functions.  Also, we have only used the eNOC 0301, not the eNOC 0311, so there may be differences in behaviour from what I am expecting.

Can you enable 'port mirroring' on a port, and plug in laptop with Wireshark to inspect the Modbus packets for the working CPU vs not working eNOC?  I use Wireshark all the time for weird stuff like this.  It may provide evidence to help diagnose.  I also make extensive use of 'Modbus Tester' from laptop to interrogate the device, using Wireshark to monitor the exchange.

[Ricard]

see you 😉