wilamowski-b-m-irwin-j-d-industrial-communication-systems-2011

Industrial Ethernet 37-7
TABLE 37.1 (continued)
“Industrial Ethernet” Outlined in Thick Black Lines
Communication Profiles (CP) in IEC 61784
IEC 61158 Types Corresponding to CP
Family
CPFs Technology Name 61784 Parts CP Number
Type
Number
15 MODBUS•-
RTPS
To avoid saturation phenomena of the network traffic due to cyclic multi-cast over UDP, Ethernet/IP
requires that the network components implementing the IGMP standard (RFC 3376 [17]) for filtering
multi-cast and 802.1Q, support for VLANs.
37.3.2 Foundation Fieldbus High-Speed Ethernet
FF HSE is developed by the Fieldbus Foundation for process control [20].
FF HSE is an application protocol (layer 7 of the OSI model) that uses UDP/IP rather than TCP/IP for
communications in “real time,” and TCP/IP for other exchanges.
FF HSE is an adaptation of the Foundation Fieldbus for Ethernet. It keeps the same data model oriented
for process applications.
FF HSE includes a real protocol for managing the “SNCC-oriented” physical redundancy. It allows the physical
redundancy of machines and ports, in contrast to the redundancy offered by the logical ring topologies.
FF HSE implements scheduling communications to ensure that two components do not publish their
data at the same time. This mechanism is implemented in the application layer to enable the use of
standard Ethernet and TCP/IP protocols. With FF HSE, it is possible to achieve a cycle time of 100.ms.
37.3.3 SERCOS III
2, 5-12 CP 15/1 MODBUS TCP 15
2, 5-12 CP 15/2 RTPS 15
16 SERCOS 1, 5-16 CP 16/1 SERCOS I 16
1, 5-16 CP 16/2 SERCOS II 16
2, 5-16 CP 16/3 SERCOS III 19
SERCOS III is supported by SERCOS trade associations [19].
SERCOS III translates the application layers of SERCOS fieldbus on Ethernet and implements mechanisms
similar as EtherCAT. It focuses on hard real-time applications, in particular, motion control.
To obtain deterministic cycle time guaranties, this solution only uses Ethernet cables (category 4,
Section 37.2.3), and is based on a daisy chain topology where only one frame circulates from devices to
devices. This frame contains data from and for all devices. There is one master by-chain, which sends
the frame all the required data to be read by slaves in a given place. Then, the devices receive this frame
one after the other, read the data they need, and write data if necessary.
Recently, SERCOS International (parent organization of SERCOS trade associations) joined the
Open Source Automation Development Lab (OSALD) [24]. This promises an open source version of
SERCOS III.
37.3.4 “Exotic Solutions”: EPA, Tcnet, Vnet/IP, PNET on IP
These last four solutions are less known either because they are not supported by one major automation
vendor (EPA and PNET on IP) or because vendors mainly use them as internal communication protocols
for their own products (Tcnet and Vnet/IP).
Ethernet for plant automation (EPA) is supported by the Chinese industry. It is built on the standard
Ethernet layers (802.3 and 802.2 or Ethernet II) and adds a top layer called EPA communication scheduling
management entity (ECSME). This layer manages network traffic on a macro cycle consisting of a periodic
transfer phase and an aperiodic transfer phase. The regularity of traffic is based on synchronization
of equipment by IEC 61588 (PTP).
© 2011 by Taylor and Francis Group, LLC