ALTUS Nexto NX3004 User Manual

6. Redundancy with NX3030 CPU
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Starting state. This condition isn’t analyzed if the project automatic synchronization is disabled (
Project Synchronization Disabling section)
 The other PLC is in Active state and firmware version of this PLC is incompatible with the
firmware version of the Active PLC
Transition 11 – Stand-by to Inactive
 NX4010 module not detected in the bus, or its microprocessor failure
 The INACTIVE button was pressed on the PX2612. This is made typically in order to execute a
programmed maintenance in the Non-Active CPU. Any programmed maintenance must be
avoided in the Stand-by CPU, thus is recommended to switch to Inactive mode
 The other CPU is in Active state. However the redundant data synchronization or the redundant
forcing list synchronization services haven’t worked in last four cycles of the MainTask or the
diagnostics synchronization service haven’t worked in the last two cycles of the MainTask
 The other PLC is in Active state. However, this PLC can’t monitor traffic in every PROFIBUS
network configured as vital fail mode
 The other CPU is in Active state, However, this CPU detected failure in Ethernet ports
configured as Vital Failure mode
Transition 12 – Stand-by to Active
 The other CPU state is unknown due to NETA and NETB failures. In this case, besides going to
Active state, for safety reasons, this CPU switches off the other CPU using the PX2612 relay.
When the Redundancy does not use PX2612 panel and there isn’t PROFIBUS DP, the CPU uses
a Keep Alive mechanism through NX3030’s NET1/NET2 ports, to intercommunicate the state
between PLCs and detect that the ACTIVE one isn’t controlling the process anymome The other
CPU state is known and different than Active
First Instants in Active State
In the first 2 seconds in Active state, as already described in PX2612 Redundancy Command Panel
Functions section, the LED ACTIVE blinks and remains on after this time has passed.
While the LED ACTIVE blinks, several transitions which, usually, could take the CPU from the
Active state, aren’t analyzed (see previous sub-sections that define transitions from the Active state).
E.g. during this time, it doesn’t work to press the STAND-BY button to try and make the CPU go to
Stand-by state.
Only two conditions allow the CPU to go out of the Active state while the LED ACTIVE blinks.
They are the following
 This PLC was switched off or restarted (warm reset, cold reset or origin reset), causing a
transition to Not-Configured state.
 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
Furthermore, in the very first instants that a PLC assumes the Active state, some non-redundant
diagnostics may not be valid, such the diagnostics of the NX5000 and NX5001 modules. The method
used to ignore the diagnostics possibly invalid is described in section Reading Non-Redundant
Diagnostics.
Common Failures which Cause Automatic Switchovers between Half-Clusters
In this section, the more common failures which, automatically, cause a switchover from the Active
CPU to Non-Active and from Stand-by CPU to Active CPU are listed. These failures trigger a sub-
group of those transitions examined in the Transition between Redundancy States section.
 Power supply fault in the Active CPU. It’s important that both CPUs have redundant power
supplies, in order to avoid that a power supply failure doesn’t affect the Stand-by CPU

ALTUS Nexto NX3004 Specifications

General

Brand	ALTUS
Model	Nexto NX3004
Category	Processor
Language	English