Siemens SIMATIC NET PROFIBUS Owner's Manual page 385

6ZB5530–3AC30–0BA1 Infrared Link Modul (ILM)
If no display indicates an error and communications problems nevertheless occur, check the parameters set on
both PROFIBUS nodes. You should also check the electrical RS 485 wiring. The most common cause of
problems is activating or deactivating the terminating resistor incorrectly. You should also check that the cable
shields at the ends of all PROFIBUS cables and all shielded power supply cables are making satisfactory
contact.
Note
Remember that sporadic data errors on the cable network are not detected by the PROFIBUS ILM. The
PROFIBUS ILM cannot check the contents of frames but can only monitor the basic functions and optical
transmission quality.
43
Copyright by Siemens