QUESTION:  
What is the monitoring time for a S7-300 CPU on the PROFIBUS when a DP slave is not available?

ANSWER:  
You are operating a PROFIBUS network with DP slaves on the PROFIBUS interface of your CPU and during Startup you wish to check whether the expected configuration matches the actual configuration. There are two different times given in the Properties dialog of the CPU, in the Startup tab.

Fig. 1: Startup properties of the CPU

An S7-300 CPU waits the time for transfer of the parameters to the modules until it checks whether there is a difference between the expected configuration and the actual configuration. If at this point in time one of the DP slaves is not available and there should not be startup if there is a difference between the expected configuration and the actual configuration, then the CPU goes into STOP mode. In this case the CPU has to be set back into the RUN mode when all the DP slaves are available.