Configuring a Network

Subnets

You can connect an S7-400 device to various subnets:

Via a Simatic Net CP Ethernet to an Industrial Ethernet subnet Via a Simatic Net CP PROFIBUS to a PROFIBUS-DP subnet Via the integrated multipoint interface to an MPI subnet

Via the integrated PROFIBUS-DP interface to a PROFIBUS-DP subnet With the M7-400, an MPI or PROFIBUS-DP network can be configured in the same way. Only the modules required for connection to the PROFIBUS-DP network are different (see Section 8.7.6).

Same Configuration

We recommend you use the same bus components as for a PROFIBUS-DP network configuration when configuring an MPI network. The same configuration rules apply.

Multipoint Interface (MPI)

This interface of the CPU uses a Simatic S7-specific protocol for data exchange with programming devices (via STEP 7), operator panels, and other S7 CPUs. The bus structure corresponds to that of the PROFIBUS.

Configuring Communication

In order that the individual nodes of an MPI or PROFIBUS-DP network can communicate with each other, you must assign MPI or PROFIBUS-DP addresses to them. The Manual Configuring Hardware and Communication Connections STEP 7 V5.0 describes how to assign these addresses and what you must take into account.

All the CPU-related data you need to know to configure communication can be found in the Reference Manual, Chapter 4.

长沙工控帮教育科技有限公司整理

Networking

5-3

S7-400 and M7-400 Programmable Controllers, Installation Manual C79000-G7076-C424-01

5.2 Fundamentals

Station = Node

Declaration: All the stations you connect in a network are referred to as nodes in the following.

Segment

A segment is a bus cable between two terminating resistors. A segment can contain up to 32 nodes. Furthermore, a segment is limited by the permissible cable length according to the transmission rate.

Transmission Rate

MPI/DP PROFIBUS DP

19.2 kbps 9.6 kbps 500 kbps

187.5 kbps (default) 19.2 kbps 1.5 Mbps

1.5 Mbps 45.45 kbps 3 Mbps

3 Mbps 93.75 kbps 6 Mbps

6 Mbps 187.5 kbps 12 Mbps

12 Mbps

Note

If you change the parameter assignment of the MPI/DP interface transmission rate, the new transmission rate remains set even after memory reset, voltage failure or removing/inserting the CPU.

Connectable Nodes

MPI PROFIBUS DP

Programming devices (PGs) Programming devices (PGs) Operator panels (OPs), WinCC Operator panels (OPs)*

S7-400/M7-400 PROFIBUS-DP master:

S7-300/M7-300 PROFIBUS-DP slaves

* Not recommended in DP operation

长沙工控帮教育科技有限公司整理

www.gkbpx.com

Number of Nodes

MPI PROFIBUS DP

127 127 *

(default: 32) of which: 1 master (reserved)

1 PG port (reserved) 1 PG port (reserved)

125 slaves or other masters

* Observe the CPU-related maximum numbers in the Reference Manual, Chapter 4

MPI/PROFIBUS-DP Addresses

In order for all nodes to be able to communicate with one another, you must assign them an address:

In the MPI network, an MPI address

A PROFIBUS-DP address in the PROFIBUS-DP network

Default MPI Addresses

The following table shows the default MPI address and the max. MPI address with which the devices are shipped:

Node (Device) Default MPI Address Default Highest MPI Address

Programming device 0 32

OP 1 32

CPU 2 32

Note

If you change the parameter assignment of the highest MPI address of the MPI/DP interface, the new address remains set even after memory reset, voltage failure or removing/inserting the CPU.

Rules for MPI Addresses

Observe the following rules before assigning MPI addresses:

All MPI addresses in an MPI network must be different.

The highest possible MPI address must be w the highest actual MPI address

长沙工控帮教育科技有限公司整理

Networking

5-5

S7-400 and M7-400 Programmable Controllers, Installation Manual C79000-G7076-C424-01

Communication from PG/OP to Module without MPI

If one of the programming devices or operator panels connected to a multipoint interface (MPI) communicates with an S7-400 module which does not have an MPI connection (for example, SINEC CPs, FM 456 etc.), this module can be reached via the CPU to whose MPI the programming device or operator panel is connected.

In this case, the CPU simply acts as an intermediary for the transfer. This type of connection between a programming device or operator panel and a module only communicating via the communication bus occupies two connection resources in the CPU.

CPU CP or FM

MPI

C bus PG or OP

Two connection resources occupied in the CPU

S7-400 station

One connection resource occupied One connection

resource occupied

Figure 5-1 Communication between Programming Device/Operator Panel and a Module without MPI

Maximum Number of Connections via MPI

When configuring the connections of a CPU 416 via MPI, remember to include the PG connection in the maximum number of possible connections.

长沙工控帮教育科技有限公司整理

www.gkbpx.com

PG Access

A CPU exchanges data with other systems using communication mechanisms, for example with other programmable controllers, with operator interface stations (OP, OS) or with programming devices (see Figure 5-2).

CPU

SIMATIC NET

MPI

PG OS PLC

PG OS Slave

PG OS PLC

DP network

Figure 5-2 Data Exchange

Process communication, including communication services for data exchange between programmable controllers (PLC – PLC) and between programmable controllers and operator interface stations (PLC – OS/OP), has priority in CPUs over communication between programming devices and CPUs.

The CPUs have different characteristics. One of these characteristics is their communication performance. If the communication resources of a CPU are occupied completely by process communication, this can severely hamper access to the CPU from the programming device.

长沙工控帮教育科技有限公司整理

Networking

5-7

S7-400 and M7-400 Programmable Controllers, Installation Manual C79000-G7076-C424-01