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ifm
Device Manual SmartSPS AC14 with EtherNet/IP interface (AC1421, AC1422), Firmware 3.1.2
2015-11-30
Glossary of Terms
the master has read the configuration data
of the CTTx slaves
the field buses can use the gateway
(optional)
the PLC program was started (optional).
>
Process image
Process image is the status of the inputs and
outputs the PLC operates with within one
→cycle.
At the beginning of the cycle the PLC
reads the conditions of all inputs into the
process image.
During the cycle the PLC cannot detect
changes to the inputs.
During the cycle the outputs are only
changed virtually (in the process image).
At the end of the cycle the PLC writes the
virtual output states to the real outputs.
>
Profibus
PROFIBUS (
Pro
cess
Fi
eld
Bus
) is a standard
for
→fieldbus communication in automation
technology. There are two versions of
PROFIBUS, DP being the one most widely
used.
PROFIBUS-DP (decentralised periphery)
for the control of sensors and actuators by
a central controller in manufacturing
engineering and for networking of several
controllers among each other. Data rates
up to 12 Mbits/s on twisted two-wire cables
and/or fibre optics are possible.
PROFIBUS-PA (process automation) is
used for the control of measurement
devices by a process control system in
process technology and is suited for
hazardous areas (zones 0 and 1). Only a
limited current flows on the bus cables in
an intrinsically safe circuit so that even in
case of a problem no explosive sparks can
occur. A disadvantage of PROFIBUS-PA is
the relatively slow data transfer rate of
31.25 Kbits/s.
>
Profinet
PROFINET (
Pro
cess
Fi
eld
Net
work) is the
open Industrial Ethernet Standard of Profibus
& Profinet International (PI) for automation.
Profinet uses TCP/IP and IT standards, is
real-time Ethernet compatible and enables the
integration of fieldbus systems.
The Profinet concept has a modular design, so
that the user can choose the functionality
himself. This is basically different as regards
the type of data exchange, to meet the
requirements regarding the speed.
For Profinet, there are the two perspectives
Profinet-CBA and Profinet-IO:
Profinet-CBA (Component Based
Automation) is intended for the
component-based communication via
TCP/IP and the real-time communication
for real-time requirements in modular plant
construction. Both ways of communication
can be used in parallel.
Profinet-IO has been created for real-time
(RT) and synchronous communication IRT
(IRT = isochronous real-time) with the
decentralised periphery. The designations
RT and IRT only describe the real-time
characteristics in the communication within
Profinet-IO.
>
R
Redundant
Redundancy is the presence of more than the
necessary means so that a function unit
performs a requested function or that data can
represent information.
Several kinds of redundancy are distinguished:
Functional redundancy aims at designing
safety-related systems in multiple ways in
parallel so that in the event of a
→failure of
one component the others ensure the task.
In addition it is tried to separate redundant
systems from each other with regard to
space. Thus the
→risk that they are
affected by a common interference is
minimised.
Finally, components from different
manufacturers are sometimes used to
avoid that a systematic fault causes all
redundant systems to fail (
→diverse
redundancy).