How and when are Modbus points polled?
EcoStruxure Building Operation
- Building Operations Enterprise Server
- Building Operation Automation Server
Need to understand the Modbus poll mechanism
Consult the 'Modbus Deep Technical Reference' chapter of EcoStruxure Technical Reference Guide
Or use WebHelp to find information on the Modbus Poll Manager, which manages all polling of the points/data and devices, and the Poll List which contains all the current subscriptions (eg. data being referenced within Programs, Listviews, Graphics, Logging, etc)
These mechanisms isolate the Modbus Polling from programs and graphics.
- For each network, the poll manager operates with a poll list and a poll task.
- If a Modbus Object value is only required for logging purposes, then the "Requested poll interval" is set to a high number (typically 2,147,483,647 ms) This means the object values are not currently being polled.
When the time arrives for the log value to be collected, the "Requested poll interval" is set to 1000ms, until the value is collected, at which point it reverts to this higher number.