ifm
Device manual AS-i M4 Gateway Profibus DPV1 (AC1375, AC1376)
2012-02-23
Glossary of Terms
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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.
More information
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.
More information
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).
The software of redundant systems should
differ in the following aspects:
specification (different teams),
specification
language,
programming (different teams),
programming
language,
compiler.
Remanent
Remanent data is protected against data loss
in case of power failure.
The operating system for example
automatically copies the remanent data to a
flash memory as soon as the voltage supply
falls below a critical value. If the voltage supply
is available again, the operating system loads
the remanent data back to the RAM memory.
The data in the RAM memory of a controller,
however, is volatile and normally lost in case of
power failure.
RTC
RTC =
R
eal
T
ime
C
lock
Provides (batter-backed) the current date and
time. Frequent use for the storage of error
message protocols.
RTS
RTS =
R
un
T
ime
S
ystem
Runtime systems are basic versions of
