Netbiter Ethernet I/P Driver and Strings

Ewon Support Ewon Netbiter
#1

Hi, I know this is a common topic but wanted to know if anyone has actually found what the class, instance and attribute are to be able to use string data types with the AB Ethernet I/P driver in the way described in the Argos administration manual.

We have a mutual client who was demonstrated the Netbiter by Routeco and HMS and has chosen it for the project, but is using a Compactlogix processor and needs to input order numbers with characters. The Compactlogix does not have native Modbus and the Rockwell sample code to implement this is heavy on memory.

I have proven the data type over Modbus using a different Rockwell PLC and have proven the principle using the string in the identity object which these devices support (Name), so if I could just find out the details above I think with SLC mapped tags in the PLC I could implement the requirements in a simple way.

Thanks for your help.

Jon

#2

Hello @jon16384,

The Netbiter is able to read data from Ethernet/IP devices using the class, instance, and attribute using the Get_attribute_single and Set_Attribute_Single. This is done using UCMM and is not a class 1 or 3 connection. UCMM also know as unconnected messaging sends explicit messages for data from the device. This is used to read data from slave devices requesting specific objects. As far as I know this is not companionable with PLC’

We also have support for accessing data from some plc’s via tag names with the Read_Tag_Service, and Write_Tag_Service. This is only available on some PLC’s and you will need to check and ensure your PLC support this. This should be compatible with Compact logic PLC’s, I have used it on a 1769-L24ER.

This would be a concern since we do not have sting support with the Netbiter. Using the Service tag option we have 16 bit signed, 32 bit signed, 32 bit unsigned, 8 bit signed, Bool, and floats. You would not be able to read in a string.

Here is a screen shot from page 21 of the Netbiters User manual showing the Ethernet/IP client support. image

#4

Hi Deryck,

Thanks for getting back to me, I guessed we might end up here.

So because the CIP service on the Ethernet driver is the single get and set attribute we can’t read multiple registers?

I am able to read the name from the identity object in all the PLCs:-

image001.png842×986 77.3 KB

image002.png1122×70 8.15 KB

Presumably because it is a single attribute, but the multiple address mentioned in the Argos manual only really relate to the Modbus driver :-

image003.png1748×270 39.2 KB

I know your service on the ethernet tag driver can’t access strings either, so Modbus is really the only one that’s of any use?

It’s a shame as it really is only the same as accessing data tables in a Micrologix or SLC controller, I have already written a function to create a string from the ascii characters held in each byte of the registers and tested it using the Modbus driver.

Thanks again,

Jon

#5
#6

Hi Jon,

Yes in this case you are just reading a single attribute for the identity. I had forgotten he Get/Set Attribute supports strings. Technically you should be able to read any attribute from the PLC, but I am not aware of a way to create and object from that accesses tag data from a PLC.

I found this post for a ethernet/IP tool regarding something similar: https://github.com/EPICSTools/etherip/issues/2#issuecomment-197316872

Deryck