The below cases explain the behavior of the system during different use cases.
Basic diagnosis information is provided for each case⮫ “Diagnosis”.
Case 1 a): Primary PLC is powered off or crashes
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Reaction |
Switchover to secondary PLC. The communication interface modules are updated by the new primary PLC. |
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Comment |
CI52x outputs are frozen during switchover period. |
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Diagnosis message on function block |
Primary PLC is powered off. Secondary PLC: control block output Runtime Error = 16#001E and xHaModPrimary = TRUE |
Case 1 b): Primary PLC is stopped
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Reaction |
Switchover to secondary PLC. The communication interface modules are updated by the new primary PLC. |
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Comment |
CI52x outputs are frozen during switchover period. |
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Diagnosis message on function block |
Primary PLC is stopped. Secondary PLC: control block output Runtime Error = 16#0016 and xHaModPrimary = TRUE |
If “lifecom2” is lost and the PLC is in STOP mode RUNTIME ERROR will not be TRUE. This is because Modbus is still responding even if PLC is in STOP mode.
Case 2 a): Secondary PLC is powered off or crashes
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Reaction |
No switchover |
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Comment |
Process continues |
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Diagnosis message on function block |
Primary PLC: control block output Runtime Error = 16#001E and xHaModPrimary = TRUE Secondary PLC is stopped. |
Case 2 b): Secondary PLC stop
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Reaction |
No switchover |
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Comment |
Process continues |
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Diagnosis message on function block |
Primary PLC: control block output Runtime Error = 16#0016 and xHaModPrimary = TRUE Secondary PLC is stopped. |
If “lifecom2” is lost and the PLC is in STOP mode RUNTIME ERROR will not be TRUE. This is because Modbus is still responding even if PLC is in STOP mode.
Case 3: Primary PLC loses connection to fieldbus CI52x modules
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Reaction |
Switchover to secondary PLC. The communication interface modules are updated by the new primary. |
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Comment |
CI52x outputs are frozen during the switchover period. |
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Diagnosis message on function block |
Primary PLC: control block output Runtime Error = 16#0094 and xHaModPrimary = FALSE Secondary PLC: control block output Runtime Error = 16#0015 and xHaModPrimary = TRUE |
Case 4: Secondary PLC loses connection to fieldbus CI52x modules
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Reaction |
No switchover |
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Comment |
Process continues |
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Diagnosis message on function block |
Primary PLC: control block output Runtime Error = 16#0015 and xHaModPrimary = TRUE Secondary PLC: control block output Runtime Error = 16#0094 and xHaModPrimary = FALSE |
Case 5: CI52x is powered off or stopped
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Reaction |
No switchover |
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Comment |
Process continues |
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Diagnosis message on function block |
Primary PLC: control block output Runtime Error = 16#0081 and xHaModPrimary = TRUE Secondary PLC: control block output Runtime Error = 16#0081 and xHaModPrimary = FALSE |
If any CI52x-MODTCP module is powered off and on, there is no need to power restart the complete system. The module will be recognized once the communication is reestablished.
Case 7 a): Dual Sync enabled - Sync connection is broken between the PLCs
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Reaction |
No switchover |
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Comment |
Process continues |
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Diagnosis message on function block |
Primary PLC: control block output Runtime Error = 16#0014 / 16#0094 and xHaModPrimary = TRUE Secondary PLC: control block output Runtime Error = 16#0014 / 16#0094 and xHaModPrimary = FALSE |
Case 7 b): Dual Sync disabled - “lifecom2” connection is lost between the PLCs
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Reaction |
No switchover |
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Comment |
Process continues by transmitting sync data via the other onboard port . |
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Diagnosis message on function block |
Primary PLC: control block output Runtime Error = 16#4096 and xHaModPrimary = TRUE Secondary PLC: control block output Runtime Error = 16#4096 and xHaModPrimary = FALSE |
Case 7 c): “lifecom2” connection is lost between the PLCs
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Reaction |
No switchover |
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Comment |
Process continues |
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Diagnosis message on function block |
Primary PLC: control block output Runtime Error = 16#0008 and xHaModPrimary = TRUE Secondary PLC: control block output Runtime Error = 16#0008 and xHaModPrimary = FALSE |
Case 8: Primary PLC loses SCADA connection
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Reaction |
No switchover |
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Comment |
Process continues, SCADA is responsible to detect and switchover |
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Diagnosis message on function block |
Primary PLC: control block output Runtime Error = 16#0000 and xHaModPrimary = TRUE Secondary PLC: control block output Runtime Error = 16#0000 and xHaModPrimary = FALSE |
Case 9: Secondary PLC loses SCADA connection
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Reaction |
No switchover |
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Comment |
Process continues, SCADA is responsible to detect and switchover |
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Diagnosis message on function block |
Primary PLC: control block output Runtime Error = 16#0000 and xHaModPrimary = TRUE Secondary PLC: control block output Runtime Error = 16#0000 and xHaModPrimary = FALSE |
SCADA link may be combined with sync connection or “lifecom2” connection. In that case runtime error and system behavior will be as described in the cases above (Sync connection lost / “lifecom2” connection broken).
Case 11: Manual changeover by user
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Reaction |
Changeover from primary PLC to secondary PLC. |
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Comment |
CI52x outputs will be frozen during switchover |
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Diagnosis message on function block |
Primary PLC: control block output Runtime Error = 16#0000 and xHaModPrimary = FALSE Secondary PLC: control block output Runtime Error = 16#0000 and xHaModPrimary = TRUE |
A manual switchover can be triggered from both PLCs. For each trigger a switchover from primary PLC to secondary PLC will take place.