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Industry 4.0 and Beyond | ADI
This calculation assumes no other traffic on the network or
that the network is managed to enable priority access for time-
sensitive traffic. It is also somewhat protocol dependent, with
slight variations in the calculation being introduced depending
on the exact Industrial Ethernet protocol used. Referring back to
Figure 2, in a machine system with cycle times down to 50µs to
100µs, the frame transmission to the furthest node can take up
to almost 50 percent of the cycle, reducing the time available to
update the motor control and motion control algorithm calculations
for the next cycle. Minimizing this transmission time is important
for performance optimization, as it allows longer and more
complex control calculations. Given that delays associated with
data on the wire are fixed and related to the bit rate, utilizing low
latency components, such as the ADIN1200 PHY and the fi do5000
embedded switch, is key to performance optimization, especially
as node count increases (for example, 12-axis CNC machine) and
cycle times reduce. Moving to gigabit Ethernet dramatically reduces
the impact of bandwidth delay but increases the proportion of
overall latency introduced by the switch and PHY components. For
example, a 12-axis CNC machine on a gigabit network will have a
network transmission delay of approximately 7.5µs. The bandwidth
element of this is negligible, and it makes little difference whether
minimum or maximum Ethernet frame sizes are used. The network
delay is split approximately equally between the PHYs and the
switches. This underlines the value in minimizing the latency in
these elements as industrial systems move toward gigabit speeds,
control cycle times reduce (EtherCAT® has demonstrated 12.5µs
cycle times), and node count expands with the addition of Ethernet-
connected sensors in the control network and the flattening of
network topologies.
Conclusion
In high-performance, multi-axis, synchronized motion applications,
control-timing requirements are precise, deterministic, and
time-critical, with a requirement to minimize end-to-end latency,
especially as control cycle times get shorter and control algorithm
complexity increases. Low-latency PHYs and embedded cut-
through switches are important elements in optimizing these
systems. To address the challenges outlined here, Analog Devices
has recently released two new robust Industrial Ethernet PHYs, the
ADIN1300 (10Mb/100Mb/1Gb) and ADIN1200 (10Mb/100Mb). To learn
about ADI's Chronous™ portfolio of Industrial Ethernet solutions and
how they are accelerating real-world Industrial Ethernet networks,
visit analog.com/chronous.
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