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Modbus RS-485 limitation on a 511, 527, 701, 711, 721, 731 and 913


Modbus values are not not working reliably and are not updating as expected.

Product Line

Andover Continuum, TAC INET, TAC Vista


Xenta controllers 511, 527, 701, 711, 721, 731 and 913


The amount of Modbus points being polled is excessive for the controller.


The product data sheets indicates no limit to the Modbus points but only 31 Modbus devices over RS-485.

With a practical install, a limit of 300-400 Modbus points per Xenta server  would be applicable. If you exceed this level, communications become slower than acceptable.

Network performance can be affected when a large number of connection objects are in use ( direct transfers between Modbus and other protocols). There is no documented limitation, but the recommendation is not to exceed 300 connection objects per Xenta Server.

Connection polling period should also be considered with a large amount of connection objects.

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Revision #:
2 of 2
Last update:
‎2018-12-13 06:21 AM
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