6. REDUNDANCY WITH NX3030 CPU
6.3.6.3. 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:
Both synchronization services previous to this cycle (Diagnostics and Commands Exchange) must be completed with
success
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
Both projects (2 CPUs) must be identical, except when the project automatic synchronization is disabled (see Project
Synchronization Disabling) section
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 syn-
chronization 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.
6.3.7. 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.
6.3.7.1. 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 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:
Project application (executable code)
Project archive (source code)
Users and groups
Access rights
Trace
The synchronization service will start within thirty seconds after one of the CPUs goes to Active state, and after its begin-
ning, 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.
Besides keeping the projects synchronized, the Project Synchronization will also avoid the Non-Active CPU to assume
superior states in relation to Starting in case the CRC is different or some Online Change is to be executed in the Active CPU.
ATTENTION
A project synchronization will have the same effect as a download in the Non-Active CPU.
This service isn’t executed if the automatic Project Synchronization is disabled, as it’s de-
scribed on Project Synchronization Disabling section.
No synchronization service between PLCA and PLCB works in case the synchronism chan-
nels cables are inverted. E.g. to connect the NETA channel in the NETB channel from PLCB
and the NETB from the PLCA in the NETA in the PLCB.
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