Modbus TCP/IP question GE to Control Techniques

Hello,

I am trying to read registers from my servo drive and I am having problems.

I set up a Modbus TCP driver in Proficy ME that is pointing to the servo drive. The register I am trying to read is Position feedback, which should be a REAL data type. When the motor moves, I see the data changing in my PLC but it is in a DINT type form. Meaning, when the motor position is 0.01 mm the value in the PLC is 65536.

I believe this is due to the fact that the drive is putting the feedback position register into two different registers. My question is how do I format the value in Proficy ME to read both registers.

For example, the drive is putting the position feedback value in 30001 and 30002. How can I format the variable in PME? 30001 - 30002 or 30001.2?

Any input?

Are you reading the Modbus data with an HMI target using a communications driver or a PLC target using a COMREQ instruction? Is the feedback data a 32-bit integer or 32-bit floating point?

I am reading the Modbus data with an HMI target using a communications driver. The feedback data is a 32 bit floating point. I found on GE's help that to read consecutive registers you put " -D" after the first register. So to read 30001 and 30002, you map your register as 30001 -D

I tried this and PME will not except this format.

Thanks for the response,
Steve

There are two possible ModbusTCP communications drivers in PME and they handle data differently.
There is a Modbus TCP/IP selection under "View Native Drivers" as well as under "View OPC Drivers". Which one did you use?

The "-D" suffix only applies to the Quick Panels (the original Total Control Products units), not to Quick Panel View/Control units.

If you used the Native Driver, you may need to read the 3xxxxx as two separate words and write a script to do the conversion. That driver uses a prefix of 8xxxxx to read a 32-bit float from two consecutive 4xxxxx Modbus registers, but it looks like it can only read the 3xxxxx register as 16-bit integers. You might want to try using the OPC driver instead.

Also, make sure you have attached the 3xxxxx address to a variable of type REAL.

I am using "View OPC Driver" Modbus TCP/IP.

Thanks,
Steve