A01900 alarm in siemens 6RA80 DC Drive indicate Configuration telegram error. This means a controller attempts to establish a connection using an incorrect configuring telegram.

1. Check the bus configuration on the master and the slave sides.
2. Check the list of the drive objects with process data exchange (p0978).
3. Check the number of data words for output and input to a drive object.
4. Check the setting in p8839 and p8815.
5. Check for inserted but not configured CBE20