Thanks everyone.
Neither the CLX nor ML1100 versions of the MSG instruction support the direct transfer of ML1100 String data to the Control Logix system.
The ML1100 COP instruction does not allow me to move the String data directly to an Integer file. I was able to move the data using independent MOV instructions. e.g.
MOV ST9:0.len N14:0
MOV ST9:0.data[0] N14:1
MOV ST9:0.data[1]N14:2
... etc.
I am able to send Integer data from the ML1100 system to the CLX system without any issues.
Just out of curiosity, if I try to read the integer data from the CLX side of the link, do I have to worry about data integrity? Or does the ML1100 protect the string/integer data file from outside influences during the execution of its rungs.