Basic Function Principles

The KL6021-0023 serial communication terminal connects the KL6023 EnOcean receiver module with the Beckhoff Bus Terminal system. EnOcean ( permits radio transmission without either batteries or an external power supply to the transmitter.

Basic Function Principles 1:
KL6021-0023 and KL6023

Approval of EnOcean radio technology


Nature and source of the danger

The KL6032 EnOcean receiver module can be operated in the following countries without registration and fees.
Permission for use in other countries must be clarified explicitly!

    • European union
    • Switzerland

    Reading received telegrams

    When the KL6021-0023 has received new telegrams it indicates this by setting the bit SB.2 in the status byte to 1. Reading out received telegrams is initiated through bit CB.0 in the control byte being inverted by the higher-level controller. The change from 0 to 1 or from 1 to 0 always causes the next telegram in the memory to be displayed in the process data. The value of the bit CB.0 is adopted by SB.0 as acknowledgement.

    The leading synchronization byte and the closing checksum are part of the EnOcean standard, and the KL6021-0023 filters them out of the telegram, so that the displayed data starts with the telegram header and ends with the status field.

    Longer telegrams

    If the telegram from an EnOcean transmitter consists of more than 4 data bytes, it cannot be transferred in a single K-bus cycle. In that case, the KL6021-0023 sets bit SB.1 in the status byte in the next read cycle, placing the next data block from the telegram into the process data.

    Faulty telegrams

    The KL6021-0023 calculates the checksum for every EnOcean telegram that is received. If this does not agree with the checksum that has been transmitted the terminal sets bit SB.6 in the status byte. A telegram is not then placed into the data memory, and is lost.

    Data memory overflow

    If the telegrams received by the KL6021-0023 are not read by the higher-level controller, the terminal's receive memory will overflow, and it will set bit SB.3 in the status byte. It is also possible for a telegram only to be partially written into the memory. This will automatically cause an error in the checksum, and it will be displayed and handled accordingly.


    The following table illustrates the general structure of an EnOcean telegram:

    Bit 7

    Bit 0


    Sync_Byte1 (0xA5)

    Synchronization byte

    Sync_Byte0 (0x5A)



    Header identification

    H_Seq (3 bit)

    • 0 unknown transmitter ID received
    • 1 known transmitter ID received
    • 2 new transmitter learnt

    Length (5 bit)

    • Number of byte following the header (here: 11)


    Telegram type

    Data Byte 3

    Data byte

    Data Byte 2

    Data Byte 1

    Data Byte 0

    ID Byte 3

    32 bit transmitter ID

    ID Byte 2

    ID Byte 1

    ID Byte 0


    Status field

    Check Sum

    Checksum (LSB resulting from the addition of all bytes, not including the synchronization byte or the checksum itself)