Rockwell Automation 1769-ASCII Compact I/O ASCII Module - Manual (Page 69)

Rockwell Automation Publication 1769-UM012B-EN-P - January 2014 69
Configure the 1769-ASCII Module Chapter 2
The 1769-ASCII module returns text data entered into Outdata tag back
to your screen.
This is not an echo program. Input is received and stored in a string file
Indata (ST11:0). New data triggers the output from another file Outdata
(ST11:1). The data back on the terminal is not the same as the data sent
from the terminal. You must put in a data string in Outdata (ST11:1)
before running the program.