Commissioning
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AutomationSystem S7-400 Hardwareand Installation
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6.9 Starting Up a PROFIBUS-DP Subnet
Introduction
This section describes the procedure for starting up a PROFIBUS-DP subnet with
an S7-400 CPU as the DP master.

Requirements

Before you can start up the PROFIBUS-DP subnet, the following requirements
must be met:
•The PROFIBUS-DP subnet has been set up (see Chapter 5).
•With STEP 7, you have configured the PROFIBUS-DP subnet and assigned a
PROFIBUS-DP address and the address area to all nodes (see manual
Configuring Hardware and Communication Connections with STEP 7). Note that
for some DP slaves, address switches must also be set (see the reference
manuals for the particular DP slaves).

Starting Up

1. Usethe programming device to load the configuration of the PROFIBUS-DP
subnet created under STEP 7 (preset configuration) in the CPU. This procedure
is described in the manual Configuring Hardware and Communication
Connections with STEP 7.
2. Switchon all DP slaves.
3. Switchthe CPU from STOP to RUN.

Behavior of the CPU During Startup

During startup, the CPU compares the preset and actual configurations. Youset
the duration of the test with STEP 7 in the “Startup” parameter block with the
“module time limits” parameter.(See also Reference Manual, Chapter 1, the
manual Configuring Hardware and Communication Connections with STEP7 ,and
theSTEP7OnlineHelp).
If the preset configuration = actual configuration, the CPU goes into RUN.
If the preset configuration ≠actual configuration, the CPU’s reaction depends on
the setting of the parameter for “Startup if preset configuration ≠actual
configuration”:
Startup if Preset Config. Actual
Config. = Yes(Default)
Startup if Preset Config. ≠Actual Config. = No
CPU goes into RUN The CPU remains at STOP and, after the timeset in the “module time
limits” parameter,the BUSF LED flashes.
Flashing of theBUSF LED indicates that at least one slave will not
respond. In this case, check whether all slaves are switched on or
display the content of the diagnostic buffer
(see Configuring Hardware and Communication Connections with
STEP 7).