Problem with communication protocol Johnson Controls N2-Bus

We have a problem reading the problem stations with this protocol. It can spend 20+ min on a non-communicating station.

We would need:

A station that loses communication - to read a certain number of invalid points - ideally if it could be set in the protocol parameters, then skip the station and read on. He is currently trying to read the whole station and it will kill a lot of time.

The customer also complains to us that in case of problems with communication at the station, metering point is invalid and the last value is stuck there. When you click on a value in HI, the value is invalidated. If there is a communication problem, it should be invalidated immediately.

Version D2000 - 10.01.039


This seems like a new feature request to me.

Do you think about a workaround? How about connecting all stations to a structured variable and monitoring their status?

If the station is e.g. more than 10 minutes (or an hour … I don’t know the time parameters of a specific application) in the ComErr or HardErr state, you can disable the communication by using tell command STSTAT STOP StationName (

Then, it will not cause problems. And you can try sometimes (again with a script) to see if it is not active.

In the Johnson Controls N2-Bus protocol, the MaxErrors parameter has been added. If the number of errors in one reading cycle reaches MaxErrors, further I/O tags will not be read. The default value of 0 disables this behavior.