Direct Communication Using Cpu 31X-2; Direct Data Exchange - Siemens SIMATIC S7-300 Series Reference Manual

CPU 31x-2 as DP Master/DP Slave and Direct Communication
2.7

Direct Data Exchange

As of STEP 7 V 5.x you can configure "Direct Data Exchange" for your PROFIBUS
nodes. The CPU 31x-2 can take part in direct communication as the sender or
receiver.
"Direct communication" is a special communication relationship between
PROFIBUS-DP nodes.
Principle
Direct communication is characterized by the fact that the PROFIBUS-DP nodes
"listen in" to find out which data a DP slave is sending back to its DP master.
Using this function the eavesdropper (receiver) can directly access changes in the
input data of remote DP slaves.
In your configuration with STEP 7, specify via respective peripheral input
addresses the address area of the receiving station to which requested send data
is fetched.
A CPU 31x-2 can be:
Transmitter operating
Receiver operating
Example:
Figure 2-10 shows an example of the direct communication "relationships" you can
configure. The figure shows all DP Masters and DP Slaves as CPU 31x-2. Note
that other DP Slaves (ET 200M, ET 200X, ET 200S) can only operate as
transmitters.
CPU
31x-2
PROFIBUS
CPU
31x-2
as DP
slave 1
Figure 2-10

Direct Communication using CPU 31x-2

2-32
as DP Slave
as DP Slave or DP Master, or as CPU that is not
tied into a master system (see Figure 2-10).
DP master system 1
CPU 31x-2 as
DP master
1
CPU
31x-2
as DP
slave 2
PLC S7-300, CPU Specifications CPU 312 IFM to CPU 318-2 DP
DP master system 2
CPU 31x-2 as
DP master
2
DP slave CPU
3 31x-2
as DP
slave 4
DP slave
5
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