Ethernet - Beckhoff BK9105 Documentation

Product overview
Up to 64 Bus Terminals can be used in a terminal block, with optional K-bus extension for up to 256 Bus
Terminals. This count does include potential feed terminals, but not the end terminal.
Bus Couplers for various fieldbus systems
Various Bus Couplers can be used to couple the electronic terminal strip quickly and easily to different
fieldbus systems. It is also possible to convert to another fieldbus system at a later time. The Bus Coupler
performs all the monitoring and control tasks that are necessary for operation of the connected Bus
Terminals. The operation and configuration of the Bus Terminals is carried out exclusively by the Bus
Coupler. Nevertheless, the parameters that have been set are stored in each Bus Terminal, and are retained
in the event of voltage drop-out. Fieldbus, K-bus and I/O level are electrically isolated.
If the exchange of data over the fieldbus is prone to errors or fails for a period of time, register contents (such
as counter states) are retained, digital outputs are cleared, and analog outputs take a value that can be
configured for each output when commissioning. The default setting for analog outputs is 0 V or 0 mA. Digital
outputs return in the inactive state. The timeout periods for the Bus Couplers correspond to the usual
settings for the fieldbus system. When converting to a different bus system it is necessary to bear in mind the
need to change the timeout periods if the bus cycle time is longer.
The interfaces
A Bus Coupler has six different methods of connection. These interfaces are designed as plug connectors
and as spring-loaded terminals.
2.5

Ethernet

Ethernet was originally developed by DEC, Intel and XEROX (as the "DIX" standard) for passing data
between office devices. The term nowadays generally refers to the IEEE 802.3 CSMA/CD specification,
published in 1985. Because of the high acceptance around the world this technology is available everywhere
and is very economical. This means that it is easy to make connections to existing networks.
There are now a number of quite different transmission media: coaxial cable (10Base5), optical fiber
(10BaseF) or twisted pairs (10BaseT) with screen (STP) or without screen (UTP). Using Ethernet, different
topologies can be built such as ring, line or star.
Ethernet transmits Ethernet packets from a sender to one or more receivers. This transmission takes place
without acknowledgement, and without the repetition of lost packets. To achieve reliable data
communication, there are protocols, such as TCP/IP, that can run on top of Ethernet.
Basic principles
The Internet Protocol (IP)
The internet protocol (IP) forms the basis of this data communication. IP transports data packets from one
device to another; the devices can be in the same network, or in different networks. IP here looks after the
address management (finding and assigning MAC-IDs), segmentation and routing. Like the Ethernet
protocol, IP does not guarantee that the data is transported - data packets can be lost, or their sequence can
be changed.
TCP/IP was developed to provide standardised, reliable data exchange between any numbers of different
networks. TCP/IP was developed to provide standardised, reliable data exchange between any numbers of
different networks. Although the term is often used as if it were a single concept, a number of protocols are
layered together: e.g. IP, TCP, UDP, ARP and ICMP.
Transmission Control Protocol (TCP)
The Transmission Control Protocol (TCP) which runs on top of IP is a connection-oriented transport protocol.
It includes error detection and handling mechanisms. Lost telegrams are repeated.
12 Version: 2.0.0 BK9055 and BK9105