Image Processing Reference
In-Depth Information
TABLE . Performance Indicators for PROFINET IO
Performance Indicator
Profiles / and /
Profile /
Delivery time
 ms
 ms
Number of end-stations


Number of switches between end-stations


Throughput RTE
. M octets/s
. M octets/s
Non-RTE bandwidth
.%
.%
Time synchronization accuracy
<
ms
<
µs
Non-time-based synchronization accuracy
Redundancy recovery time
<
 ms
 ms
as standard Ethernet switches. In this addresses-based phases, RT frames are transmitted followed
by NRT Ethernet frames (see also Figure .). All PROFINET switching devices are synchronized
by means of a modified IEEE  mechanism with on the fly stamping [], to have their cycles and
IRT timetables synchronized with  µs jitter.
PROFINET CBA and IO do not need any special hardware for RT communication. To ensure
good performance, PROFINET IO needs a  Mbps switched full duplex Ethernet network. For
IRT, a special PROFINET-Ethernet switch is needed. It is recommended to integrate this special
PROFINET-Ethernet switch in every device to allow all possible Ethernet network topologies as
listed in Table ..
The PROFINET specification includes a concept allowing one to integrate existing fieldbuses with
proxy devices. A proxy device represents a field device or a fieldbus with several field devices, on
the PROFINET network. he user of the PROFINET does not see any difference, if the device is con-
nected to Ethernet or to the ieldbus. his proxy technology is very important to allow for a migration
of the existing fieldbus installations to new Ethernet solutions with PROFINET. Initially, proxies are
defined for INTERBUS (type  in IEC ) and PROFIBUS (type  in IEC) but today proxies
are also defined for DeviceNet, AS-Interface, and other networks in the field.
21.5 Summary: Conclusions
During the standardization process there was a long discussion on why is it not possible to reduce the
number of technical solutions to three or four RTE profiles. But there was a common understanding
from the manufacturers that it is not up to the engineers in the standardization groups to take such
decisions. It is agreed, that the market should decide which system will be successful in the field. So
the problem of selecting a good solution is finally moved to the end user. We will see which of the
RTEsystemsintheinternationalstandardwillstillbeinlargeusageinthenexttoyears.
References
. Felser,M.andSauter,T.,heieldbuswar:Historyorshortbreakbetweenbattles? IEEE Interna-
tional Workshop on Factory Communication Systems
(
WFCS
)
,Västerås,Sweden,August-,,
pp. -.
. IEC , Digital data communications for measurement and control—Fieldbus for use in industrial
control systems, , available at www.iec.ch.
. IEC -, Digital data communications for measurement and control, Part : Profile sets for contin-
uous and discrete manufacturing relative to fieldbus use in industrial control systems, , available
at www.iec.ch.
. Decotignie, J.-D., Ethernet-based real-time and industrial communications, Proceedings of the IEEE ,
(), June , -.
. IEC -: Industrial communication networks—Profiles, Part : Additional fieldbus profiles for
real-time networks based on ISO/IEC -, available at www.iec.ch.
 
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