equipments on profibus stopping due to communication fault
we have a 800xA DCS in our plant. I/O network is on profibus. Now some I/O equipments whose profibus hardware is in one controller but their control logic in written in a different controller with signal exchange between the above two plc via MMS messaging. PLCs are communication via profinet on a redundant control network. Now above mentioned equipments started tripping frequently on communication fault , profibus loop checking was done and found ok. On checking systems alarms and events, multiple events like "connection to plc lost, data storm detected" was logged. Problem got sorted out when primary control network switch was turned off and plc communication continued via secondary control network switch . System has now run successfuly for 48hrs since the secondary control network switch is working. can someone help me identify what can be the problem.