2. EtherCAT embeds its payload/frame into
standard Ethernet frame. The frame is
identified with the Identifier(0x88A4) in the
EtherType field. Since the EtherCAT protocol
is optimized for short cyclic process data, the
use of protocol stacks, such as TCP/IP or
UDP/IP, can be eliminated.
3. EtherCAT has its header and telegram.
Master creates oringinal frame and sends it to
each slaver.
Each slaver will take out or provide packet
when frame go through it.
4. Datagram header indicates what type of
access the master device would like to
execute:
• Read, write, read-write
• Access to a specific slave device through direct
addressing, or access to multiple slave devices
through logical addressing (implicit addressing).
5. EtherCAT’s telegram contains many sub-
frames.
Safety over EtherCAT frame is important to
EtherCAT to protect data, device, or other
essentials.
6. Purposes:
• A single communication system for both control and
safety data.
• The ability to flexibly modify and expand the safety
system architecture.
• Pre-certified solutions to simplify safety applications.
• Powerful diagnostic capabilities for safety functions.
• Seamless integration of the safety design in the
machine design.
• The ability to use the same development tools for both
standard and safety applications.
7. FSoE is part of SCL (Safety
Communication Layer)
It is based on application layer, part of OSI.
And it also developed according to IEC
61508, is TÜV certified, and is
standardized in IEC 61784-3. The protocol
is suitable for safety applications with a
safety integrity level up to SIL 3.
8. EtherCAT generally has two safety
protocol controllers for redundant.
Safety protocol controller generates the
FSoE frame.
9. EtherCAT uses a single channel to transfer
both standard(non-safe) and safety-
critical(safe) data. This communication
system is part of a “Black Channel”.
Black channel is not considered to be
safety-relevant.
10.
11. IEC 61508-2:2010 clause 7.4.11 offers white channel and a black
channel approaches and refers the user to IEC 61784-3 or the IEC
62280 series.
White channel approach means the entire network including the
communication devices at both ends are developed to the relevant
functional safety standards. This would be a lot of work and limit the
use of standard networking components.
Black channel is the more common approach, where no
assumptions are made about the channel and safety is taken care of
with an additional SCL (Safety Communication Layer) in the
application software. This SCL is developed to the safety standards
but everything else in the communication system is just a standard
component. The picture below is taken from the IEC 61784-3
standard.
12. FSoE frames, known as safety containers,
contain safety-critical process data and
additional information used to secure this
data. The safety containers are transported
as part of the communication’s process
data.
13. CMD: The type of the command.
Safe Data: The safety-critical(safe) data.
Cyclic Redundancy Check(CRC): An error-detecting code.
.
.
.
14. Whether data transfer is safe does not
depend on the underlying communication
technology, Black Channel, and isn’t
restricted to EtherCAT.
