Rockwell Automation 1734-485ASC POINT I/O ASCII User Manual - Manual (Page 66)

Publication 1734-UM009B-EN-P - July 2003
B-6 Using the ASCII Modules with the ControlLogix System Application Examples
Transmitting Data from ControlLogix Through the ASCII Modules
For this example, the advanced mapping feature in RSNetWorx for
DeviceNet was used to separate the header bytes into their own data
locations. The diagram below illustrates that the transaction ID is in
Local:1:O.Data[1] and the length is in Local:1:O.Data[3]. The ASCII data
starts in Local:1:O.Data[4].