The User Data rollout appears when the USER-DEFINED FUNCTION is chosen from the Function list. It allows you to enter the contents of the custom request. Type in hexadecimal numbers (characters 0-9, A-F, either lowercase or uppercase).
The context menu offers you the following functions:
DD AA B5 (3 bytes) sequence displayed in result pane will result in bytes 0xDD, 0xAA and 0xB5 written into the output file. The resulting file can subsequently be used by some other application for additional processing.