Communication issue with Xenta devices


the communication with TAC Xenta controllers is slow or inconsistent

Product Line

SmartStruxure Solution


TAC Xenta

LonWorks communication


The Non group receiver timer is not properly set.

Every device has a timer called Non group receive timer. The Non group receive timer is used to make sure that a re-sent Lon package will not be treated as a new message and to determine when a receiver buffer can be released. It is used in Acknowledged, Repeated and Request/Response transactions, but not in Unacknowledged ones.

If this timer is set too low, a re-sent package, like Unacknowledge repeated message, may be treated as new messages, that will be sent on to the application.

The communication buffers will not be released until the timer has expired. If the timer is set too long, that may result in the device running out of buffers, and new messages will not be received during this time.

If a device has many SNVTs or TACNV’s being transferred there may be a need to increase the value of the Non group receiver timer. The default value for a programmable Xenta device is 768 ms.


Change the Non group receive timer of the Xenta devices.

The default value for a programmable TAC Xenta device is 768 ms. The recommended timer values are:


Number of network variables Non group receive timer value
< 50 768 ms (default)
50 – 100 1024 ms
> 100 1536 ms



The default value for the AS and AS-P  is 8,092 ms. There is no need to change that value.