November 2015
16
I
ndustrial
C
ontrol
& C
ommunications
MCU enables simple creation
of EtherCAT applications
By Hairuo Qiu,
Infineon Technologies
This article introduces
the microcontroller XMC4800 which
contains specialized functions
and features to simplify EtherCAT
applications. It is the first
microcontroller with an integrated
EtherCAT slave controller and
analog/mixed signal IP using
the Cortex M4 processor from ARM.
EtherCAT combines the highest demands
on isochronous determinism, bandwidth, and
interference immunity like no other real-time
Ethernet protocol. In addition the EtherCAT
development is stable, without any break:
functions at the IP core are expanded, but
always remain compatible with previous ver-
sions. Nevertheless, the market acceptance of
EtherCAT is not comparable to that of other
fieldbus systems such as CAN. The XMC4800
microcontroller may provide the foundation
to change this. This is because it combines
EtherCAT with lower implementation costs,
higher product quality, long-term availabil-
ity (until at least 2027) and a free of charge
integrated development environment that is
tailored to EtherCAT applications and the
component itself.
Global digitization is making inroads into
manufacturing and taking its toll in the form
of vast amounts of data – measurement and
control data from sensors and actuators, data
for local and remote diagnosis, and data
transferred from one machine to another. If
automation technicians are consulted about
communication at the machine and field level,
they will report that EtherCAT is an estab-
lished standard. On the other hand classic
fieldbus systems such as Profibus and CAN are
simply reaching their technical limits. They
are not able to handle such large amounts of
data because of the lack of bandwidth. And
although it is not yet clear what development
path Industry 4.0 will take, it is fairly safe to
say that the amounts of data will not diminish.
Amazingly, real-time Ethernet systems have
thus far failed to achieve universal acceptance.
The manufacturers of drives, PLCs, and I/O
modules have given various reasons for this.
For Ethernet/IP – the Rockwell standard –
many think that the lack of determinism is a
limitation, permitting cycle times in the low
single-digit microsecond range at best. The
Siemens standard, Profinet, suffers similar
limitations, at least in its RT design. The iso-
chronous Profinet IRTon the other hand has
the reputation of not being fully matured. It
took years to finalize the current version, 2.3,
interim versions are not compatible with each
other, and it remains the problem whether
version 2.3 will really be the final version.
EtherCAT, on the other hand, has not been
changed since 2004. The earliest devices com-
municate in the same network with the new-
est products despite all the new functions that
have been added in the meantime. EtherCAT
also achieves best isochronous determinism
values ranging from the three-digit to the low
two-digit nanosecond range. There is only
one property that EtherCAT so far shares
with Profinet and Ethernet/IP: relatively high
procurement and maintenance costs, the lat-
ter throughout the entire product life cycle.
So far this has been because there have been
no related highly integrated circuits. That
changes with the XMC4800 32-bit micro-
controller. The XMC4800 is the first micro-
controller with an integrated EtherCAT slave
controller and analog/mixed signal IP that
uses the Cortex M4 processor from ARM.
A comparison with established solutions based
on TI Sitara, FPGA or ASIC shows how easy it
is to implement EtherCAT with the XMC4800.
The MCU requires no additional components
such as external memory or quartz clock gen-
erator to start up the EtherCAT slave control-
ler. An integrated PLL supplies the EtherCAT
IP with the necessary 25-MHz clock. Code is
executed from the ARM Cortex M4 processor
at 144 MHz from the integrated RAM or flash
memory. The reduced costs resulting from
the reduced BOM are obvious. But external
memory in particular creates something that
is not always obvious at first glance: the dif-
ficult product maintenance during the whole
product life cycle. Memory manufacturers
optimize technologies for the PC and mobile
computing, meaning that technology nodes
becomes obsolete after five years at the latest
and are not economical thereafter. The result
is component obsolescence. This does not fit
well with the life cycles of industrial systems,
in which machine longevity of 15 years or
