BECKHOFF BK3xx0 - Manual (Page 88)

Notes on the Documentation
86 Fieldbus Components
State transitions in the Bus Coupler
If the PROFIBUS DP configuration received does match the Bus Terminal configuration in multi-configuration mode,
the Bus Coupler sets the "static diagnostics" bit in the PROFIBUS DP diagnostic data and delays the execution of a
terminal bus cycle (I/O RUN LED remains off). As soon as the terminal assignment (activated/not activated) has been
written by the PROFIBUS DP master, the Bus Coupler again carries out an examination of the PROFIBUS DP
configuration, and automatically enters cyclic data exchange (the "static diagnosis" bit in PROFIBUS DP diagnostic
data is cleared, and the terminal bus cycle is executed cyclically (the I/O-RUN LED goes on during the terminal
cycle)). Furthermore, the terminal assignment is stored in the non-volatile memory of the Bus Coupler, so that during
a restart of the PROFIBUS DP, the PROFIBUS DP master does not have to write the terminal configuration again.