BECKHOFF KL4112 - Manual (Page 14)

Register description
14 KL4112
A further example
Writing register 31 in the BK2000 with an intelligent terminal and the end
terminal.
If the following bytes (user code word) are transferred from the controller to
the terminal,
Byte0
Control
Byte1
Not used
Byte2
Data OUT, high byte
Byte3
Data OUT, low byte
0xDF 0xXX 0x12 0x35
the user code word is set and the terminal returns the register address with
the bit 7 for register access and the acknowledgement.
Byte0
Status
Byte1
Not used
Byte2
Data IN, high byte
Byte3
Data IN, low byte
0x9F 0x00 0x00 0x00