Siemens SIMATIC ET 200AL System Manual page 968

IO communication via PROFINET IO
The inputs and outputs of distributed I/O devices are read and written by means of
PROFINET IO using what is referred to as IO communication. The following figure provides
an overview of IO communication by means of PROFINET IO.
A IO controller - IO controller communication via PN/PN coupler
B IO controller - I-device communication
C IO controller - IO-device communication
Figure 2-3 IO communication via PROFINET IO
PROFINET with STEP 7 V15
Function Manual, 12/2017, A5E03444486-AH
Description
2.1 Introduction to PROFINET
21