6. Redundancy with NX3030 CPU
295
Transition 4 – Starting to Active
The other CPU is in Non-Active state. Before the transition is possible, this condition must
remain true for some time, higher to PLCB than PLCA. This way, at the moment PLCA and
PLCB are simultaneously turned on; PLCA has priority to take over in Active state
The other CPU state can’t be discovered through NETA / NETB, and besides that this CPU can’t
monitor traffic in any PROFIBUS network configured as vital fail mode, or those networks
weren’t created. Therefore, it really looks the other CPU if off or out of execution. For safety
reasons, besides switching to Active, this CPU turns the other off using its PX2612 relay. This
condition must be kept for a while before the transition is executed
Transition 5 – Starting to Stand-by
The other PLC is in Active state. The redundant data synchronization and the redundant forcing
list synchronization services are working correctly
Transition 6 – Inactive to Not-Configured
This PLC was switched off or restarted (warm reset, cold reset or origin reset) or its CPU went to
Stop mode
The STAND-BY button was pressed on the PX2612. Besides going to the Not-Configured state,
a configuration request is made. This way, the CPU goes out automatically from the Not-
Configured state for the Starting state. The user typically presses this button after repairing the
failure which has driven the CPU to the Inactive state
This PLC has its synchronization disabled and the project is different from the Active PLC, at the
STAND-BY button pressing, the PLC goes from Inactive to Not-Configured
Transition 7 – Active to Not-Configured
This PLC was switched off or restarted (warm reset, cold reset or origin reset) or its CPU went to
Stop mode
Transition 8 – Active to Inactive
NX4010 module not detected in the bus, or its microprocessor failure. This CPU knows the other
CPU was in Stand-by state before this failure happened. This condition isn’t analyzed in the first
2 seconds in Active state
This PLC has lost communication with another PLC through NETA and NETB due to an internal
failure but knows the other PLC was in Stand-by mode just before the failure occurred. This
condition isn’t analyzed in the first 2 seconds in Active state
This CPU can’t control all PROFIBUS networks configured in vital fail mode and knows the
other CPU is in Stand-by state. This condition isn’t analyzed in the first 2 seconds in Active state.
This CPU detected a total failure in Ethernet networks configured in vital failure mode, and
knows that the other CPU is in Stand-by state
Transition 9 – Active to Stand-by
Both PLCs, for some reason, are in Active state and this conflict must be solved. The PLCA
switches to Stand-by state in case this conflict remains. The PLCB does the same after a delay
smaller than PLCA. This way, in this case, PLCA has priority to remain in Active state
The STAND-BY button was pressed and this CPU knows the other CPU is in Stand-by state.
This condition isn’t analyzed in the first 2 seconds in Active state
Transition 10 – Stand-by to Not-Configured
This PLC was switched off or restarted (warm reset, cold reset or origin reset)
The other PLC is in Active state and it’s known this PLC project is different from the Active
PLC. Besides going to the Not-Configured state, a configuration request is made. This way, after
the projects synchronization, the PLC goes automatically from the Not-Configured state to the
To Next Page
Loading...