GE SNP protocol CPU identifier string

Next week I will meet a guy to update some of his SCADA database client.

When I talked to him today he asked me a question about GE SNP protocol.

He says he cannot establish the communication because he can't get the PLC CPU identifier String wright.

Here are the instruction from the help file concerning this driver.

PLC CPU identifier String. This entry may consist of up to six characters for the Series 90-30 and seven characters for Series 90-70. If configured in a multidrop network, this field has to be configured to match the PLC CPU ID. The default is a Null string which may be used to communicate to any PLC regardless of its CPU ID.

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He has a stand alone 90-70 PLC so it seems that he don't need any string in this field (null string?). Is this OK or is there some more I should pass along to him. I have never use the 90-70.

The app. is ParagonTNT5.50 SCADA