Wiring the S7-400
5.3 Rules for Configuring a Network
Rules
Observe the following rules for connecting the nodes of a network:
• Before you interconnect the individual nodes of the network, you must assign to each node the MPI address and the highest MPI address or PROFIBUS-DP address.
Tip: Mark the address of each node in a network on the housing. To do this, use the adhesive labels enclosed with the CPU. You can then always see which address is assigned to which node in your plant.
• Before you insert a new node in the network, you must switch off its supply voltage.
• Connect all the nodes in the network in a row. In other words, include the fixed programming devices and operator panels directly in the network.
Only use spur lines for connecting the programming devices / OPs to the network which are needed for startup or maintenance.
• If you operate more than 32 nodes in a PROFIBUS-DP network, you must connect the bus segments via RS 485 repeaters.
In a PROFIBUS-DP network, all bus segments together must have at least one DP master and one DP slave.
• You connect ungrounded bus segments and grounded bus segments via RS 485 repeaters (see Reference Manual CPU Data, Chapter 10).
• The maximum number of nodes per bus segment decreases with each RS 485 repeater. This means that if there is an RS 485 repeater in a bus segment, there may only be a maximum of 31 other nodes in a bus segment.
However, the number of RS 485 repeaters has no effect on the maximum number of nodes on the bus.
Up to ten segments can be connected in series.
• Switch on the terminating resistor at the first and last node of a segment.
To ensure the bus operates without interference, you should not switch off these nodes.
长沙工控帮教育科技有限公司整理
Networking
5-8 Automation System S7-400 Hardware and Installation
A5E00850741-01
Data Packets in the MPI Network
Observe the following feature in the MPI network:
Note
If you connect an additional CPU to the MPI network during operation, data may be lost.
Remedy:
1. Disconnect power from the nodes to be connected.
2. Connect the nodes to the MPI network.
3. Switch on the nodes.
Recommendation for MPI Addresses
Reserve MPI address “0” for a service programming device and “1” for a service OP, which will later be briefly connected to the MPI network as required. Thus you assign different MPI addresses to the programming devices / OPs incorporated in the MPI network.
Reserve MPI address “2” for a new CPU. You thus avoid the duplication of MPI addresses after a CPU with a default setting has been installed in the MPI network (for example, when replacing a CPU). Thus you assign an MPI address higher than
“2” to all CPUs in the MPI network.
Recommendation for PROFIBUS-DP Addresses
Reserve PROFIBUS-DP address “0” for a service programming device, which will later be briefly connected to the PROFIBUS-DP network as required. Thus you assign other PROFIBUS-DP addresses to all the programming devices
incorporated in the PROFIBUS-DP network.
Components
You connect the individual nodes via bus connectors and the PROFIBUS-DP bus cable. Remember to provide a bus connector with PG female port for nodes into which a programming device may be plugged if required.
Use RS 485 repeaters for the connection between segments and for extending the cable.
长沙工控帮教育科技有限公司整理
Networking
Automation System S7-400 Hardware and Installation 5-9
A5E00850741-01
Terminating Resistor on the Bus Connector
on off on
off
Terminating resistor switched on
Terminating resistor switched off
Figure 5-3 Terminating resistor on bus connector
Terminating Resistor on the RS 485 Repeater
DC24 V
L+ M PE M 5.2
A1 B1 A1 B1
A2 B2A2 B2 SIEMENS RS 485-REPEATER
ON
ON Terminating resistor for bus segment 1
Terminating resistor for bus segment 2
Figure 5-4 Terminating resistor on RS 485 repeater
长沙工控帮教育科技有限公司整理
Networking
5-10 Automation System S7-400 Hardware and Installation
A5E00850741-01
Example: Terminating Resistor in the MPI Network
The figure below shows where you have to connect the terminating resistor in a possible configuration for an MPI network.
RS 485 repeater {
{
{
{ Terminating resistor switch on
S7-400 S7-400
S7-400
Spur line
S7-300
OP OP
PG
Programming device
Figure 5-5 Terminating resistor on MPI network
长沙工控帮教育科技有限公司整理
Networking
Automation System S7-400 Hardware and Installation 5-11
A5E00850741-01
Example of an MPI Network
* Only connected via spur line for startup/maintenance (with default MPI address)
** Connected to the MPI later on (with default MPI address) 0 ... x MPI address of nodes
{ Terminating resistor switch on
S7-400** S7-400 S7-400 S7-400
S7-400 S7-400
0
11 10 9 8 7
1
2 3 4 5 6
OP OP
OP** PG
{ {
S7-300
Programming device
Figure 5-6 Example of an MPI network
长沙工控帮教育科技有限公司整理
Networking
5-12 Automation System S7-400 Hardware and Installation
A5E00850741-01
Example of a PROFIBUS-DP Network
0 ... x PROFIBUS DP addresses of nodes S7-400 with
CPU 414-2-DP
as DP master ET 200M
0 8 7 6
1 2 3 4 5
PG*
OP
ET 200M PG S5-95U
ET 200B ET 200B
{
{
{ Terminating resistor switched on
* Only connected via spur line for startup/maintenance (with default PROFIBUS-DP address = 0)
Figure 5-7 Example of a PROFIBUS DP network
长沙工控帮教育科技有限公司整理
Networking
Automation System S7-400 Hardware and Installation 5-13
A5E00850741-01
Example Using a CPU 414-2
The figure below shows an example of a configuration with CPU 414-2 DP which is integrated in an MPI network and simultaneously used as DP master in a
PROFIBUS-DP network.
In both networks, the node numbers can be assigned separately without conflicts resulting.
OP S7-400
S7-400 with CPU 414-2 as
DP master ET 200M
ET 200B
* Only connected via spur line for startup/maintenance { Terminating resistor switched on
MPI network PROFIBUS-DP network
Figure 5-8 Example with CPU 414-2
长沙工控帮教育科技有限公司整理
Networking
5-14 Automation System S7-400 Hardware and Installation
A5E00850741-01
Programming Device Access Beyond Network Limits (Routing)
You can access all modules beyond network limits using a programming device.
ET 200
PROFIBUS-DP network 2
Programming device / PC 2 Programming device / PC 3
Programming device / PC 1
MPI network 1
S7-400 with CPU 417 S7-400 with
CPU 416
S7-300 with CPU 318
S7-300 with CPU 318 MPI network 3
Figure 5-9 Programming device access beyond network limits Requirements :
• Use STEP 7 from version 5.0 onwards
• Assign STEP 7 to a programming device or PC on the network (SIMATIC Manager, Assign programming device/PC)
• The network limits are bridged by modules with routing capability.
长沙工控帮教育科技有限公司整理
Networking
Automation System S7-400 Hardware and Installation 5-15
A5E00850741-01