BECKHOFF BK3xx0 - Manual (Page 85)

Notes on the Documentation
Fieldbus Components 83
Process image interfaces
The interfaces between controller, PROFIBUS DP master interface, Bus Coupler and Bus Terminals form process
images, in which the process signals are stored according to certain algorithms:
The process signals of a DP slave (Bus Coupler BK3110, BK3120 or BK3520) are always transferred in a
Data_Exchange telegram, in which the outputs are sent by the DP master and the inputs are received in the
associated telegram response. In the PROFIBUS DP master interface, the process images exchanged with the Bus
Couplers are mapped to the process images of the control according to a mapping rule.