Example - Manual - SIMATIC AX - System.Serialization - System.Serialization,

USING System.Serialization;

FUNCTION SerDe_Demo
    VAR_TEMP
        data : ARRAY[0..5] OF BYTE;
        nextValueOffset: UDINT;
    END_VAR

    // data = [0x0, 0x0, 0x35, 0x12, 0x0, 0x0]
    // nextValueOffset = 4
    nextValueOffset := SerializeLittle(UDINT#2, UINT#16#1235, data);
END_FUNCTION