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Object list
Octet
OV
P
Page addressing
Passive nodes
PDU
PII
PIQ
Process image
PROFIBUS
PROFIBUS–DP
Protective conductor
Protocol Data Unit
R
Reference earth
Reference potential
Repeater
ET 200U Distributed I/O Station
EWA 4NEB 812 6087–02b
Data communications on the bus cannot commence unless the FMS
master is informed of the stations involved and their significance and
structure. This information is contained in the object list (OV).
The object list of the ET 200U(DP Standard/FMS) contains the follo-
wing:
Input and output values of the ET 200U(DP Standard/FMS)
Diagnostics data
Parameter data.
Octet is a general expression for one byte.
Object list
Multiplying of address range
They may exchange data with an active node only after being reque-
sted to do so by the active node (= slave station).
Protocol Data Unit
Process image
Process image
An "image" of the input states (= PII) or output states (= PIQ) at a spe-
cified point of time. The process image can be accessed by the PLC
program.
PROcess FIeld BUS, German process and field bus standard defined in
the PROFIBUS standard (DIN 19245).
It specifies functional, electrical and mechanical characteristics for a
bit–serial field bus system.
PROFIBUS–DP draft standard (DIN 19245, Part 3) on which the
ET 200 distributed I/O system is based.
The major task of PROFIBUS–DP is the fast cyclic data exchange
between the central master stations and the I/O devices.
A conductor required for protective measures against shock currents. It
is symbolized by PE.
A protocol data unit (PDU) contains the information to be exchanged
between two bus nodes.
In the PROFIBUS specification, this means a message exchanged, for
example, between the ET 200U(DP Standard/FMS) and the FMS ma-
ster.
The maximum length of a protocol data unit is specified in the
of communications links.
Earth
Potential to which the voltages of the circuits involved are referred, or
with reference to which they are measured.
Device for amplifying bus signals and interfacing
ering long distances.
Glossary
list
segments for cov-
B-5
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