General Max-On Rx3I Considerations; Improving Ethernet Sync Efficiency Using Plc Sweep Mode - Emerson PACSystems RX3i User Manual

User Manual
GFK-2409B
Appendix A System Consideration
A-1

General Max-ON RX3i Considerations

There are several considerations and recommendations that should be taken into account
when defining a Max-ON RX3i system. This appendix summarizes the main items that the
application developer should keep in mind when planning and developing such a system.
1. Ethernet Synchronization LAN should use dedicated Ethernet Interface Modules. If
2. Ethernet I/O LANs should use dedicated Ethernet Interface Modules and be isolated
A-2 Improving Ethernet Sync Efficiency Using PLC
Sweep Mode
For the Ethernet Synchronization interfaces to work efficiently, it is necessary to extend the
Scan Time in one or both PLCs. The extra time is used to transfer Synchronized Variables
through the CPU Communications Window. There are two approaches. Each has its own
advantage.
Automatic Mode Selection
In this approach, the system detects which CPU is the Backup and then sets the Backup to
Constant Sweep. If there is a transfer in Mastership, then the Max-ON RX3i driver will set the
new Master CPU into Normal Sweep and the new Backup to Constant Sweep.
Why you should consider this approach:
•
•
The period for Constant Sweep is determined automatically once per second. The value is
calculated by adding 75 milliseconds to the master's Scan Time and then rounding
downward to the nearest multiple of 5 milliseconds.
To enable this mode of operation:
1. Using Logic Developer PLC, open your Max-ON RX3i Project.
2. Select the PLC_COMMON_CODE Target as the Active Target.
System Consideration
other devices such as I/O or HMIs are placed on the Sync LAN, they can have a
negative impact on the performance of the system in terms of Failover and
Synchronization time. Therefore, it is recommended that the Sync LAN be isolated.
Adding a single device like the Logic Developer PLC programmer or the Max-ON
RX3i Diagnostic tool should be acceptable and useful when diagnosing the system.
from a main Ethernet network. Again, if other devices are placed on the I/O LAN,
they can have a negative impact on the performance of the I/O system in terms of
IO update time. Therefore, it is recommended that the I/O LAN be isolated.
The Master always operates with the fastest Scan Time possible.
The Backup will adjust its timing regularly to meet current system requirements.
Appendix A
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