Datamax E-Class Mark II Programmer's Manual page 130

STX KtU Read Unique Serial Number from RFID Tag
(Direct Mode – HF [13.56 MHz] ISO15693 Tag Interface)
This command instructs the RFID device to read the unique serial number data from the
tag and then place that data into a replaceable field. It is expected that the tag
transponder will be within the read / write distance of the RFID programming device;
otherwise, "Void" will be printed in the text or bar code label field(s).

This is a sixteen character alphanumeric value; the replaceable field must have an
adequate length.
Syntax:
Where:
118
Extended System-Level Command Functions
<STX>KtUabcc<CR>
- The number of retry attempts, 0-9.
a
- Reserved. Should be 0.
b
- Field number in which to place the data (must be 01,
cc
02, 03, etc.) matching the order of Label Formatting
command, U.

A 00 value will send the ID to the host with no printing.
Class Series 2 Programmer's Manual