What are the options for communication between two IM151 CPUs?
The ET 200S with the IM151 CPU can be used as DP slave, DP master
(with DP master interface module MLFB: 6ES7 138-4HA00-0AB0) or in
standalone mode. This provides you with the following options for
1.1 S7 Basis
1.2 Global Data Communication
2. PROFIBUS DP
via an Additional DP Master
Communication via a DP Master Interface Module
1.1 MPI - S7 Basic
With the ET 200S CPU (from MLFB: 6ES7 151-7AA10-0AB0) you
can configure the internal interface as PROFIBUS or as MPI. If you
choose the MPI configuration, the S7 basic communication services
Fig. 1: Communication via a common MPI network in standalone
For communication via the MPI network as shown in Fig. 1 you can
use the blocks "X_SEND", "X_RCV", "X_GET", "X_PUT" and "X_ABORT" of
the S7 Basic Communication. The communication can be set up by both
More information on these blocks is available in the STEP 7
Online Help (Mark block in block container> Press "F1") and in
the manual "SIMATIC System Software for S7-300/400 System and
Standard Functions" in Entry ID: 1214574.
1.2 MPI - Global
With the ET 200S CPU (from MLFB: 6ES7 151-7AA10-0AB0) you can
connect the internal interface both to a PROFIBUS network and to an
For the connection via the MPI network shown in Fig. 1 you can
also realize data exchange via global data. This communication can
be set up by both stations.
The configuration of data exchange via global data is similar to
the configuration of global data for CPUs of the S7 300 or S7 400
Detailed instructions on configuring are available in the STEP 7
Online Help in the "Index" tab, keyword "Global Data Communication
DP - Communication via an Additional DP Master
Communication between two PROFIBUS slaves without DP master (see
Fig. 2) is not possible. This contradicts the PROFIBUS DP
communications principle and is thus independent of the type of DP
Fig. 2: Networking the ET 200S CPUs via PROFIBUS DP without DP
If both IM151 CPUs of the ET 200S are used as DP slaves, then
you need a separate DP master (e.g. the integrated DP interface of
an S7-300 CPU as shown in Fig. 3).
Fig. 3: Networking of the ET 200S CPUs via PROFIBUS DP with DP
If data is to be transferred from one DP slave to another slave,
then this has to be done by the DP master. The DP master reads the
data out of the DP slave and writes it to the other slave. This
communicationcannot be triggered by the CPU in the ET
DP - Communication via the DP Master Interface Module
If there is a master interface module (implementation of IM151
CPUs 6ES7151-7AA10-0AB0 and higher possible) in one of the two ET
200S modules, then you do not need a separate master. The second
IM151 CPU is then a DP slave on the master interface module of the
first ET 200S (see Fig. 4).
Fig. 4: Networking the ET 200S CPUs via PROFIBUS DP with DP
In this case, too, the communication can only be triggered by
the DP master. Transfer of data from the ET 200S CPU that is
connected as DP slave is not possible (exception: if you use
the "Direct Data Exchange" function).
In versions 2 and 3 using the PROFIBUS DP network, data exchange
via I/O access (e.g. L EW1 or T PAW6) or by calling system
functions SFC14/15 can be made from the DP master concerned in each
DP - Direct Data Exchange
Another option involves using direct data exchange (internetwork
traffic). With this function you can exchange data between two DP
slaves and between a DP master and a DP slave without having to
make any special function call-ups in the program of the DP master
or DP slave. The configuration is similar configuring the "Global
Data Communication" function.
In the case of communication between two DP slaves however, you
do need an associated DP master for each slave so that the PROFIBUS
DP network required for direct data exchange can be set up (setup
is as shown in Fig. 3). With the "Direct Data Exchange" function it
is also possible to exchange data between two slaves that do not
share a common master, but use the same PROFIBUS network.
Detailed information on "Direct Data Exchange" is available in
the STEP 7 Online Help. Refer to Entry ID : 17660809 to find out
whether your DP slave modules support the "Direct Data Exchange"
function and to what extent.
For low data transfer rates you can set up a serial
point-to-point connection between two IM151 CPUs. This
communication option depends on whether the ET 200S is being used
as DP master, DP slave or in standalone mode. For this you only
need the "interface module 1SI" (MLFB: 6ES7138-4DF*0-0AB0) in each
ET 200S station.
You can create PROFInet components for CBA (Component-based
Automation) from the stations of STEP 7. The requirement here is
that you have installed the iMap software package using the
installation option STEP 7 AddOn.
Each PROFInet component has an interface, the PROFInet
interface. With this interface the PROFInet components can
communicate with each other and with the HMI system. The interface
description is stored in a data block in STEP 7 - in the Interface
DB. When you create the PROFInet component, the structure of the
interface and the number and properties of the inputs and outputs
are taken from this Interface DB.
In the case of intelligent slaves - like the IM151 CPU of the
ET200S - the DP master does not access the connected inputs and
outputs of the slave directly, but accesses a transfer area in the
address area of the CPU. The input and output data from the
transfer area of the Interface DB of the PROFInet component is
transferred to the transfer area of the IM151 CPU. For this data
communication the Copy blocks FC10 (PN_IN) and FC11 (PN_OUT) have
to be programmed in the user program for STEP 7.
Fig. 5: Data communication between Interface DB and I/O address
FC10 copies the data from the transfer area of the DP master
with proxy functionality to the inputs of the Interface DB and FC11
copies the outputs of the Interface DB to the transfer area of the
DP master with proxy functionality.
A proxy system consists of a PROFInet device with proxy
functionality and all the PROFIBUS devices linked to it. The proxy
functionality permits a PROFIBUS device to communicate not only
with its DP master, but also with all the PROFInet communication
More information on this is available in the manual
"Component-based Automation Creating PROFInet Components " (MLFB:
6ES7820-0CC03-0YX0), which is also in the Internet in Entry ID: