Siemens S7-400 Starting Up a PROFIBUS-DP Subnet, Requirements, Behavior of the CPU During Startup

Commissioning

6.9Starting 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.Use the 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.Switch on all DP slaves.

3.Switch the CPU from STOP to RUN.

Behavior of the CPU During Startup

During startup, the CPU compares the preset and actual configurations. You set 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 STEP 7, and the STEP 7 Online Help).

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	Startup if Preset Config. ≠ Actual Config. = No
Config. = Yes (Default)
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 the BUSF 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).

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