HI 800 101 HIMatrix Engineering Manual
5.2 Ethernet Communication
5.2.1 Communication via Switches
The switch integrated into each system for safeethernet or Ethernet communication can be
seen on the block diagrams.
• In contrast to a hub, a switch is able to store data packets for a short period of time
in order to establish a temporary connection between two communication partners
(transmitter/receiver) for the transfer of data. In this way, collisions (typical of a hub)
can be avoided and the load on the network is reduced. For controlled data transfer
every switch needs an address/port relation table. This table will be automatically
generated in a self-learning process. Each port in the switch is correlated to defined
MAC addresses. According to this table incoming data packages are directly swit-
ched to the corresponding port.
• The switch automatically switches between the transfer rates of 10 and 100 Mbit/s
and between full and half duplex connections. This makes the full bandwidth avail-
able (full duplex operation) in both directions.
• A switch controls the communication between different devices. The switch can ad-
dress up to 1000 absolute MAC addresses.
• Autocrossing recognizes that cables with crossed wires have been connected, and
the switch adjusts accordingly.
Note
When configuring the safety-related communication in accor-
dance to the HIMatrix manual, the information contained in the
Safety Manual must be regarded.
5.2.2 Safeethernet
In the field of automation central themes are requirements like determinism, reliability, chan-
geability, enlargement and over all safety.
Safeethernet provides a transfer protocol for transmitting safety-related data up to SIL 3 on
base of the Ethernet technology.
Safeethernet implements mechanism that can detect and react safety-related on the follow-
ing faults:
• Corruptions of the transmitted data (duplicate, lost, changed bits)
• Wrong addresses of messages (transmitter, receiver)
• Wrong sequence of data (repetition, lost, change)
• Wrong timing (delay, echo)
Safeethernet is based on the standard Ethernet or FastEthernet according to IEEE802.3.
The transmission of the safety-related data uses the protocol frame of the standard Ethernet.
According to the Black Channel Approach in Safeethernet "insecure transmission channels"
(Ethernet) are used and controlled by safety-related protocol mechanism at transmitter and
receiver.
In this way normal Ethernet network components like hubs, switches, routers and PCs sup-
plied with network interfaces can be used within a safety-related network.
The significant difference to standard Ethernet is determinism, the real-time ability, of safe-
ethernet. A special protocol mechanism guarantees deterministic behavior even in case of
faults or new entries of communication participants. New components are automatically inte-
grated in the running system. All components of the network could be changed while the sys-
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