Fig. 19 Counter And Startredundancymasterflag - Beckhoff FC3102 Documentation

FC310x as master
SetPrm Unlock before DP-Start-Up or SetPrm-Unlock at Shutdown (TwinCAT 2.8: see PROFIBUS [} 42]
tab of the master, TwinCAT 2.9: see Fault Settings [} 51] dialog) and perhaps the device watchdog
(TwinCAT 2.8: see FC310x [} 40] tab of the master, TwinCAT 2.9: see Fault Settings [} 51] dialog).
Primary-Master: the Redundancy Mode is not active. The settings of SetPrm-Unlock before DP Start-Up
and of SetPrm-Unlock at Shutdown should be deactivated, if there is to be no interaction on the DP slaves
when the primary master starts or stops (outputs remain unchanged). In addition, the device watchdog must
be set (TwinCAT 2.8: see FC310x [} 40] tab of the master, TwinCAT 2.9: see Fault Settings [} 51] dialog),
to ensure that the primary master logs off the bus in the event of a PC crash.
Redundancy Master: the Redundancy Mode is active. The settings of SetPrm-Unlock before DP Start-
Up and of SetPrm-Unlock at Shutdown should be deactivated, if there is to be no interaction on the DP
slaves when the primary master starts or stops (outputs remain unchanged).
There are also three counters and a StartRedundancyMasterFlag as interfaces to the PC:
Fig. 19: Counter and StartRedundancyMasterFlag
Counter[2] (ReceivedTelegram-Counter): This counter is incremented every time a valid PROFIBUS
telegram is received
Counter[3] (ReceivedTelegramFromPrimary-Counter): This counter is incremented every time a valid
PROFIBUS telegram is received from the primary master (which has the same station address as the
redundancy master)
Counter[4] (ClaimTokenTimeout-Counter): This counter is incremented every time the redundancy master
detects a timeout on the bus after it has taken over bus activity under normal circumstances, i.e. with
Redundancy mode deactivated. (ClaimTokenTimeout time = (6 + 2 * station address of the DP master) *
slot time).
StartRedundancyMasterFlag: This can be used to start or stop the redundancy master.
The application (PLC task or other program) is therefore responsible for diagnosing a failure of the primary
master (by detecting that the ReciveTelegram-Counter and the ReceivedTelegramFromPrimaryMaster-
Counter no longer increment, that the ClaimTokenTimeout-Counter increments or the user-specific
FC3101 and FC3102 Version: 3.0 39