Commissioning
S7-300 Programmable Controller Hardware and Installation
8-34 A5E00105492-01
Data Transfer in STOP Mode
The DP slave CPU goes into STOP mode: Data in CPU intermediate memory are
overwritten with "0". That is, the DP master reads "0".
The DP master goes into STOP mode: Actual data in CPU intermediate memory is
maintained and can still be read by the CPU.
PROFIBUS Address
With CPU 31x-2 DP/31xC-2 DP do not set "126" as PROFIBUS address.
8.7.4 Direct data exchange
Prerequisite
In 7 STEP 7 V 5.x or later, you can configure "Direct data exchange" for
PROFIBUS nodes. CPUs 31x-2 DP/31xC-2 DP can participate in direct data
exchange both as sending or receiving station.
Definition
"Direct data exchange" is a special communication relationship between
PROFIBUS-DP nodes.
Characteristic of direct data exchange is that PROFIBUS-DP nodes "listen" on the
bus for data a DP slave returns to its DP master. This mechanism allows "Listening
stations" (receivers) direct access to modified input data of remote DP slaves.
Address Areas
In your STEP 7 configuration of the respective peripheral input addresses, specify
which address area of the receiving station is to receive data requested from the
sending station.
A CPU 31x-2 DP/31xC-2 DP can operate as:
• DP slave sending station
• receiving station, as DP slave or DP master, or as CPU not integrated in a
master system.
Example:
The sample in the figure below shows the relationships you can configure for direct
data exchange. In the figure, all DP masters DP slaves are a CPU 31x-2 DP/31xC-
2 DP respectively. Note that other DP slaves (ET 200M, ET 200X, ET 200S) can
only operate as sending station.
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