SIEMENS
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Siemens D 11 · 2015
2
Highlights
Communication
> PROFIBUS
■
Overview
PROFIBUS – the most successful open fieldbus
in the automation environment
The requirements of users for an open, non-proprietary commu-
nication system have resulted in the specification and standard-
ization of the PROFIBUS protocol.
PROFIBUS defines the technical and functional features of a
serial fieldbus system, with which the distributed field automa-
tion devices in the lower area (sensor/actuator level) can be n-
etworked up to the mid performance range (cell level).
Standardization according to IEC 61158/EN 50170 secures your
investments for the future.
Using the conformity and interoperability test performed by the
test laboratories authorized by PROFIBUS & PROFINET Interna-
tional (PI) and the certification of the devices by PI, users have
the security of knowing that the quality and functionality is guar-
anteed, even in multi-vendor installations.
PROFIBUS versions
Three different PROFIBUS versions have been defined in order
to comply with the widely differing requirements at the field level:
PROFIBUS FMS (F
ieldbus M
essage S
pecification) – the univer-
sal solution for communication tasks at the field and cell levels in
the industrial communication hierarchy.
PROFIBUS PA (P
rocess A
utomation) – the version for applica-
tions in process automation. PROFIBUS PA uses the intrinsically
safe transmission technology specified in IEC 61158-2.
PROFIBUS DP (D
istributed P
eriphery) – this version, which is op-
timized for speed, is specifically tailored to the communication
of automation systems with distributed I/O stations and drives.
PROFIBUS DP sets itself apart as a result of very short response
times and high noise immunity, and replaces cost-intensive,
parallel signal transfer with 24 V and measured value transfer
utilizing 0/4 … 20 mA technology.
■
Design
Bus participants on PROFIBUS DP
PROFIBUS DP makes a distinction between two different master
classes and one slave class:
DP master class 1
For PROFIBUS DP, DP master class 1 is the central component.
In a defined and continually repeating message cycle the cen-
tral master station exchanges information with distributed sta-
tions (DP slaves).
DP master class 2
Devices of this type (programming, configuring or operator con-
trol devices) are used during commissioning, for configuring the
DP system, for diagnostics or for operating the active plant or
system. A DP master class 2 can, for example, read input, out-
put, diagnostic and configuration data of the slaves.
DP slave
A DP slave is an I/O device which receives output information or
setpoints from the DP master, and as response, returns input in-
formation, measured values and actual values to the DP master.
A DP slave never sends data automatically, but only when re-
quested by the DP master.
The quantity of input and output information depends on the de-
vice, and for each DP slave in each send direction can be a max-
imum of 244 bytes.
■
Function
Functional scope in DP masters and DP slaves
The functional scope can differ between DP masters and DP
slaves. The different functional scopes are classified as DP-V0,
DP-V1 and DP-V2.
DP-V0 communication functions
The DP-V0 master functions consist of "Configuration", "Parame-
ter Assignment" and "Reading Diagnostics Data", as well as cy-
clic reading of input data/actual values and writing output data/
setpoints.
DP-V1 communication functions
The DP-V1 function expansions make it possible to perform acy-
clic read and write functions as well as processing cyclic data
communication. This type of slave must be supplied with exten-
sive parameterization data during start-up and during normal
operation. These acyclically transferred parameterization data
are only rarely changed in comparison to the cyclic setpoints,
actual values, and measured values, and are transferred at
lower priority in parallel with the cyclic high-speed user data
transfer. Detailed diagnostic information can be transferred in
the same way.
DP-V2 communication functions
The extended DP-V2 master functions mainly comprise func-
tions for isochronous operation and direct data exchange be-
tween DP slaves.
•
Isochronous mode:
Isochronous mode is implemented by means of an equidistant
signal in the bus system. This cyclic, equidistant clock signal
is sent by the DP master to all bus nodes in the form of a global
control frame. Master and slaves can then synchronize their
applications with this signal. The signal jitter between cycles
is less than 1
μ
s.
• Slave-to-slave:
The "publisher/subscriber" model is used to implement slave-
to-slave communication. Slaves declared as publishers make
their input data/actual values and measured values available
to other slaves, the subscribers, for reading. This is done by
sending the response frame to the master as a broadcast.
Slave-to-slave communication is therefore a cyclic process.
PROFIBUS with SINAMICS
SINAMICS uses the PROFIBUS DP protocol.
The SINAMICS drives can only be used as DP slaves.
G_PM10_XX_00144
© Siemens AG 2015