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Entry type: Product note Entry ID: 6847578, Entry date: 02/27/2001

New: Y Link to Connect Single-Channel DP Masters to S7-400H

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The new Y Link provides a network transition from a redundant DP master system of a S7-400H PLC to a single-channel DP master system. It permits the connection of devices with only one PROFIBUS DP port to S7-400H systems as switched I/Os.

Towards the PLC, the Y Link is a DP slave and towards the network a DP master.

The Y Link has the order no. 6ES7 197-1LA00-0XA0) and consists of the following components:

IM 157 (2 of)

6ES7 157-0AA81-0XA0

IM 157 Bus module

6ES7 195-7HE80-0XA0

Y Coupler

6ES7 654-0YK00-0AB0

Bus-module coupler

6ES7 654-7HY00-0XA0


6ES7 972-0AA01-0XA0

In addition, a 24 V load power supply and a standard mounting rail for active bus modules are required to design a Y link.
Mounting rails are available in the following lengths:

19" (482 mm)

6ES7 195-1GA00-0XA0

530 mm

6ES7 195-1GF30-0XA0

620 mm

6ES7 195-1GG30-0XA0

2 000 mm

6ES7 195-1GC00-0XA0

Features of the Y Link:

  • Modular design on S7-300 standard mounting rail with active backplane bus
  • All transmission rates, from 9.6 Kbits/s to 12 MBaud for the redundant DP master system
  • Bump-free switching of the active channel of the redundant DP master system
  • Support of configuration changes during operation of a S7-400H system
  • Diagnostics via LEDs and via the user program
  • Transmission rate of 187.5 Kbits/s to 1.5 Mbit/s for the subordinated DP master system (independent of the DP master system)
  • Galvanic isolation between subordinated DP master system and power supply via RS 485 repeater

Method of operation

The Y Link reproduces the subordinated DP master system as switched DP slave on the S7-400H.
The Y coupler and the subordinated DP master system form an independent bus system and operate decoupled from the redundant bus system.
The Y Link as DP slave on the redundant DP master system acts as deputy for the parties of the subordinated DP master system, with respect to the data.


The Y Link can be configured with STEP 7 version 5.1 SP1 or higher.
When the bus parameters are calculated by STEP 7, the connected parties of the subordinated DP master system, as well as the Y Link itself, are taken into consideration.

Configuration possibilities

A S7-400H system can be expanded with Y Links as follows:

  • The number of Y Links is only limited by the maximum number of bus parties.
  • In each Y Link only one Y coupler can be operated. DP/PA couplers cannot be operated in the Y Link.
  • The number of parties in each subordinated DP master system is limited to 31. The sum of the slots is limited to 223.
  • The max. configuration message frame length and the max. message frame lenght for I/O data are 244 bytes for each Y Link.
  • The ET 200M distributed I/O system should not be connected to a redundant DP master system via Y Link, but via IM153.
  • The Y Link can only be used with S7-400H in redundancy mode.

Quantity framework of the Y Link

Connectable DP slaves

max. 31

Occupied slots

223 (one DP slave can occupy a number of slots)

Message frame length for diagnostics

168 bytes (188 bytes for interrupts)

Message frame length for parameterization

18 bytes

Message frame length for configuration

max. 244 bytes

Message frame length for user data

max. 244 bytes of outputs and
max. 244 bytes of inputs

Communications conections
from PG/PC to Y Link
from PG/PC to DP slaves (routing)

5 connections
10 connections

Parametrization of the DP slaves via PG/PC

For parameterization of the DP slaves, a PG/PC can be connected either to the redundant or to the subordinated DP master system.

DP Slaves that cannot be connected

  • The following DP slaves cannot be operated on a Y Link:
    - Operator panels and text displays
    - DPV1 slaves


The documentation of the Y Link is contained in the manual DP/PA Bus Coupling and Y Link.

Order no.:


6ES7 157-0AA00-8AA0


6ES7 157-0AA00-0BA0

Additional information is available under the following attachment:

PI_Y-Link.pdf ( 257 KB )

Your SIMATIC contact at your local Siemens office will answer any further questions you may have.

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