user manual

Equipment Description
50
33003405 07/2007
SafeEthernet
Overview This section provides information about SafeEthernet protocol and OSI model.
Description In the field of automation, requirements, such as determinism, reliability,
interchangeability, extensibility, interoperability and the overall safety are central
themes. Based on the Ethernet technology, SafeEthernet provides a transfer
protocol for transmitting safety-related data up to RC 6 or SIL 3. SafeEthernet
implements a mechanism that can detect and react to the following:
l Corruption of transmitted data
l Incorrect address allocation for the messages (transmitter, receiver)
l Incorrect data sequence (repetition, loss, change)
l Incorrect timing (delay, echo)
SafeEthernet is based on the standard Ethernet or FastEthernet according to
IEEE 802.3.
The transmission of the safety-related data does not change 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. This way, regular Ethernet network components, such
as hubs, switches, routers, and PCs supplied with network interfaces can be used
within a safety-related network. The significant difference to standard Ethernet is
determinism, the real-time ability of SafeEthernet.
A special protocol mechanism ensures deterministic behavior even in case faults
occur or new communication participants emerge. New components are
automatically integrated into the running system. All components of the network
could be changed while the system is running. With the use of switches,
transmission times can be clearly defined. This way, Ethernet works in real time.
Possible transfer speed up to 100Mbit/s for safety-related data is higher than the
speed normally used. Copper lines as well as fiber optic cables can be used as
transmission media. The integration of firm intranets as well as connections to the
Internet, can be realized with SafeEthernet technology. The terms for safety-related
communication have to be considered.