Siemens SIMATIC ET 200AL System Manual page 1303

Functions
5.5 Intelligent DP slaves (I-slaves)
Difference: DP slave - I-slave
In the case of a DP slave, the DP master accesses the distributed inputs/outputs directly.
In the case of an I-slave, the DP master accesses a transfer area in the I/O address space of
the preprocessing CPU instead of accessing the connected inputs/outputs of the I-slave. The
user program running on the preprocessing CPU is responsible for ensuring data exchange
between the operand area and inputs/outputs.
Figure 5-13
Note
DP master or DP slave
Note: The communication modules of the S7-1500 CPUs/ET 200SP CPUs, for example the
CP 1542-5, support the operation as DP master or DP slave only as alternative.
Note
The I/O areas configured for data exchange between the DP master and DP slaves must not
be used by I/O modules.
80
Data access to an I-slave
PROFIBUS with STEP 7 V13
Function Manual, 12/2014, A5E03775446-AC