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Help! I've been beating my head against the wall in RemoteConnect trying to make a Modbus write to an external device use the same data conversion as the read from the same remote register. I'm new to RemoteConnect and have spent hours trying to sort this simple problem out.
PLC: SCADAPack 474, Serial Port 1
External Modbus Slave: Rotork IQ3 actuator, Modbus-RTU
My objective is to work with all values in the 474 and the Modbus-TCP-connected Red Lion HMI as REALs to avoid having to rescale integer data everywhere it is used. I am trying to have the 474 scale and unscale the values to the Rotork automatically at the Modbus scanner level. On the Modbus reads this works fine. On the Modbus writes, no matter what value is in the Logic variable, the 474 always writes a value of 6552 back to the Rotork.
The Modbus scanner in the 474 reads the register data from the Rotork properly. All the Rotork data is 16-bit UINT format.
The Device Modbus objects into which the data is being loaded are defined as T_SPx70_REAL and the scaling (in the object's Basic tab) is 10000:1000, so a raw Modbus read value of 175 becomes a real value of 17.5 for use in Logic. This all works fine when the 474 reads Modbus data from the Rotork.
However, if I change the value of the variable in the program to something else, the Modbus Scanner writes it out to the Rotork as 6552, no matter what I change it to.
I'm all but certain the issue has to do with the object definition and the related internal data type conversions (Display Format (REAL (Eng)), Logic Variable Type (T_SPx70_REAL), Modbus Data Type (UINT), but I'll be darned if I can figure it out after hours of trying.
This does not work.
I end up with this:
This does work, but only in the Online Diags window,
When the HMI writes an updated real value to the 474, 6552 gets written to the Rotork.
Thank you in advance for any assistance with this.
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