Direct Data Exchange; Principle Of Direct Data Exchange - Siemens SIMATIC S7-400 Manual

PROFIBUS DP
5.1 CPU 41x-3 PN/DP as DP master / DP slave
5.1.8

Direct Data Exchange

5.1.8.1

Principle of direct data exchange

Overview
Direct data exchange is characterized by PROFIBUS DP nodes which "listen" on the bus
and know which data a DP slave returns to its DP master.
This mechanism allows the "listening node" (recipient) direct access to deltas of input data of
remote DP slaves.
In your STEP 7 configuration, define the address area of the recipient in which the required
data of the publisher will be read, based on the peripheral input addresses.
A CPU 41x can be:
● DP slave sending station
● as DP slave or DP master or as CPU that is not linked into a master system
Example:
The following figure uses an example to explain which direct data exchange "relations" you
can configure. All the DP masters and DP slaves in the figure are 41x CPUs. Note that other
DP slaves (ET 200M, ET 200X, ET 200S) can only be senders.
PROFIBUS
Figure 5-7
5-26
(see Fig. 3-9).
CPU 41x as
CPU 41x-2
DP Slave 1
CPU 41x as
DP slave 1
Direct data exchange with 41x CPUs
DP master
System 1
DP slave 3
CPU 41x as
DP slave 2
DP master
System 2
CPU 41x as
DP Slave 2
CPU 41x as
DP slave 4
S7-400 Automation System, CPU Specifications
Manual, 10/2006, 6ES7498-8AA04-8BA0
DP slave 5