Hello, everybody

We have a communication problem with one of our station (S7-400) and an error message is displayed:

Net time required by all OB exceeds max limit

What does that mean? and what have i to do?

Thanks

Hello,

In my opinion, there is a small confusion here.

The error message is not directly related to communication by itself, even if the words "Net time" appears.
"Net" is meant here as the "netto" sum of the program runtime of the several OBs used in the program,
and does not refer to Net = network.
See picture in annex.

In other words, the program load seems higher as the alarm limit.
Of course a very high load could affect how fast a system communicates.

Thnx for answer,

So, if it is a problem of capacity so what should i do?

hi sam,

have a look in your programm where you can save cycle time. 

In the S7-400 manual you find information about all operations with their need of cycletime.

SIMATIC S7-400 S7-400 Automation System, CPU Specifications

you find it in chapter 9.2 Cycle Time Calculations

hope this helps,

regards,

Thnx for answer,

I shall do

Hello,

Nothing, the same problem repeats again,

We lose communication with all the slaves located on the same route. so it can be a cable problem (profibus).

What can i do?

sam2014

Hello,

Thanks for all answers,

We had a clamping problem.

 Mr.Sam

How did u solve this OB exceeds max limit?

Did u face problem in profibus network due to this error.

I am facing same problem when my profibus network have a disturbance then OB exceeds alarm i am getting.

Can u send details in screen shots.