6. Redundancy with NX3030 CPU
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Redundant Forcing List Synchronization
This service is responsible for the redundant forcing list transferring, from the Active CPU to the
Inactive CPU.
For this service to be executed, several conditions must be satisfied:
ï‚· Both synchronization services previous to this cycle (Diagnostics and Commands Exchange)
must be completed with success;
ï‚· In case this CPU is in Active state, the other must be in Non-Active state. On the other hand, in
case this CPU is in Non-Active state, the other must be in Active state;
ï‚· Both projects (2 CPUs) must be identical, except when the project automatic synchronization is
disabled (see Project Synchronization Disabling section);
ï‚· At least one synchronism channel (NETA and/or NETB) must be operational. If both
synchronism channels (NETA and NETB) are operational, the communication is distributed
between both (load balances) in order to reduce the synchronization time. In case only one
channel is operational, the synchronism will continue to be executed only by this channel,
keeping the redundant data synchronization.
ATTENTION:
The redundant forcing list has only forcing over redundant variables. On each CPU (PLCA and
PLCB), there can be a different forcing list related to non-redundant variables.
Sporadic Synchronization Services through NETA and NETB
The following synchronization services are executed sporadically, in other words, they are not
executed in each MainTask cycle. Another system task executes these sporadic services in
background.
Project Synchronization
This service is responsible for synchronizing the Active CPU and Non-Active CPU projects. This
happens when the projects are different in both CPUs and the automatic projects synchronization is
enabled on both CPUs.
The synchronization is always from the Active CPU to the Non-Active CPU and it’s enough that a
one out of two synchronism channel (NETA or NETB) is operational for this service to be executed.
When the synchronization is enabled, the following files and services will be synchronized:
ï‚· Project application(executable code);
ï‚· Project archive (source code);
ï‚· User and groups;
ï‚· Access rights;
ï‚· Trace.
The synchronization service will start within thirty seconds after one of the CPUs goes to Active
state, and after its beginning, the project CRC will be checked every five seconds.
When synchronization is started the Non-Active CPU goes to Stop mode, at the Not-Configured
state. After the transferring of all necessary files, the Non-Active CPU goes to Run, at Starting state.
In case the transfer fails, the CPU goes back to Not-Configured state.
The time the synchronization will take to be fully executed depends on the project size. In average, a
transfer rate between the synchronism channels is approximately 500 Kbytes/s.
In case the synchronization is interrupted (communication loss between synchronism channels)
during the files transferring from the Active CPU to the Non-Active CPU, the procedure is aborted
and restarted when the communication is restored. Only after the conclusion of the whole procedure
the Non-Active CPU goes to Run mode.
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