Especially in safety-critical applications real-time (RT) communication is a must. Ethernet networks come into the game when price is an issue and high-performance standardized protocols are needed. Fieldbusses used today are partly based on industrial real-time Ethernet variants with standardized safety protocols like Profinet, EtherCAT, Ethernet Powerlink, and others. The safe train control system family also uses a real-time Ethernet communication within the network. This piece gives answers to the following questions: 1: How is Communication within menTCS Organized? 2: Which RT Ethernet Standard is Used for menTCS? 3: Why EtherCAT for menTCS? 4: What are the Extension Possibilities for menTCS?

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Fifth Level
November 23, 2017
4 Things to Know about…
Real-Time Ethernet Communication of
Safe Train Control System menTCS

2. 2
RT Ethernet Communication of menTCS
Especially in safety-critical applications real-time (RT) communication is a must.
Ethernet networks come into the game when price is an issue and high-
performance standardized protocols are needed. Fieldbusses used today are
partly based on industrial real-time Ethernet variants with standardized safety
protocols like Profinet, EtherCAT, Ethernet Powerlink, and others.
The safe train control system family also uses a real-time Ethernet
communication within the network. This piece gives answers to the following
questions:
1: How is Communication within menTCS Organized?
2: Which RT Ethernet Standard is Used for menTCS?
3: Why EtherCAT for menTCS?
4: What are the Extension Possibilities for menTCS?

3. How is Communication within menTCS Organized?
The menTCS software distinguishes
between the safe and the non-vital
domain. In order to guarantee
appropriate communication between
the safe controller and the safe I/O
functions via real-time Ethernet, the
“black channel” approach is applied
and ensures end-to-end protection of
transmission.
In addition, up to 63 modular menTCS
I/O boxes are available to connect
remote I/Os to the central menTCS
controller.
> See data sheet of control unit MH50C

4. Which RT Ethernet Standard is Used for menTCS?
The complete menTCS I/O – no matter whether it is part of the menTCS controller
unit or located in the remote I/O boxes – are connected via real-time Ethernet
”EtherCAT“. All remote I/O boxes are connected to the controller in a ring topology,
which tolerates single failures. For example, in case of a broken cable, the system is
still fully operational, as all I/O boxes can still be reached from the other end of the
ring. The communication is protected via Safety over EtherCAT (FSOE) protocol.
> See data sheet of
remote I/O box KT8

5. Why EtherCAT for menTCS?
EtherCAT is a real-time Ethernet standard based on open Ethernet that fulfills the
conditions to make communication between menTCS components safe:
▪ EtherCAT is deterministic, with cycle times ≤ 5 ms.
▪ EtherCAT is able to operate without switches.
▪ EtherCAT supports a ring topology.
▪ The safety communication layer of EtherCAT (FSoE) establishes an end-to-end
protection to the safe I/O board.
▪ Any packet that leaves the safe domain is encapsulated in an envelope that is checked
by the receiver of the packet (the safe I/O board). With this method, failures like packet
duplication, loss, wrong sequence, corruption, wrong addressing etc. are covered.
▪ FSoE covers the requirements of EN 50159.
> Get more detailed answers to menTCS in
the Frequently asked Questions

6. What are the Extension Possibilities for menTCS?
Theoretically you can attach e.g. a standard (non-safe) EtherCAT device to
menTCS. However, with the current status of the EtherCAT software on the CPU,
there is no way to access the non-safe EtherCAT data on the IO Processor or on
the Control Processor. With a modified version of the EtherCAT master and/or the
PACY software (included in menTCS package), it is possible to support non-safe
EtherCAT devices.
You can also attach a safety EtherCAT device with FSoE from a third party to
menTCS, but it needs software support on the Control Processor, in form of a
PACY device driver.
> Get the press release for more
information about PACY
If you use a copper-to-fiber-optic converter from
a third party (e.g. Beckhoff’s CU1521 “EtherCAT
media converter fibre optic”) also fiber optic can
be used to connect to EtherCAT devices.

7. www.men.de/tcs/
www.menmicro.com/tcs/
www.men-france.fr/tcs/