Issue
An increased amount of polling caused by Modbus groups with duplicate registers.
Product Line
EcoStruxure Building Operation
Environment
- Modbus
- Building Operation Automation Server Premium (AS-P)
- Building Operation Automation Server Bundled (AS-B)
- Building Operation Automation Server (AS)
Cause
Modbus Register Groups cause multiple resisters to be requested in a single query. This can be a very efficient way of collecting data from a device. See this Article for details. However, if a register is repeated (duplicated) within a group it can cause an increased amount of polling.
The screenshots shows a Modbus Register Group with a Requested group poll interval set to 10,000ms, but the misconfiguration is forcing polls at 500ms.
Resolution
The resolution is simply to avoid such a configuration.
NOTE - If a Modbus Register Group with duplicates registers becomes unstable with some registers showing offline, then disabling the Scattered Read function will usually help.
