Profibus International (PI) is the international industrial
communications community responsible for two of the most
important technologies used in plant and process automation
today: PROFIBUS - the most popular fieldbus for discrete
manufacturing and process control and PROFINET - an 'Industrial
Ethernet' solution supporting advanced plant automation
strategies and helping them be merged easily into the
enterprise and beyond.
Tel: +49 721 9658 590
Fax: +49 721 9658 589
PROFINET is the leading Industrial Ethernet standard for
automation that includes plant-wide fieldbus communication,
plant-to-office communication, and equipment-to-equipment
integration. PROFINET can simultaneously handle standard
TCP/IP transmissions AND real-time transmissions at sub-millisecond
speeds. PROFINET embraces industry standards like Ethernet,
TCP/IP, XML, and OPC. Using proxy technology it connects
other fieldbuses in addition to PROFIBUS; thus protecting
the existing investment in plant equipment and networks.
PROFINET is more than a fieldbus - it's a means of integrating
disparate control equipment without programming! Currently
more than 100 engineers from at least 50 different companies
are working in 20 distinct Working Groups to advance PROFINET.
PROFINET is the innovative open standard for Industrial
Ethernet. PROFINET satisfies all requirements for automation
technology. With PROFINET, solutions can be implemented
for factory and process automation, for safety applications,
and for the entire range of drive technology right up
to clock-synchronised motion control.
PROFINET uses Ethernet as well as TCP, UDP, and IP as
the basis for communications. TCP/IP is the de-facto standard
for communication protocols in the IT arena. But for interoperability,
it is not enough just to establish a common communications
channel between field devices based on TCP, UDP, and IP,
because these standards merely represent the basis for
data exchange. Additional protocols and determinations
are thus needed on top of TCP or UDP, the so-called application
protocols, which ensure the interoperability of applications.
The interoperability of applications between field devices
is only ensured when the same application protocol is
being used. Typical application protocols are, for instance,
SMTP (email), FTP (file transfer), and HTTP (Web).
The different application areas in industrial automation
depend on a wide range of services for communications.
These range from non-time-critical through real time capable
to clock-synchronized. PROFINET offers therefore scalable
For non-time-critical processes, PROFINET uses Non Real
Time communication (NRT) with the standard Ethernet mechanisms
over TCP/IP or UDP/IP. This NRT communication follows
the international standard IEEE 802.3. This is enough
for most applications of process automation.
In industrial applications of factory automation, however,
significantly stronger requirements for data bandwidth
and for clock synchronization exist. Data exchange optimized
for performance is called Real Time communication (RT),
and the deterministic and clock-synchronised communications
is called Isochronous Real Time (IRT), which enables clock
rates of under 1 ms and a jitter precision of <1 Ás.
Distributed I/O (Remote I/O) is connected through PROFINET
IO. Here, the familiar I/O view of PROFIBUS is retained,
in which the user data from the field devices are periodically
transmitted into the process model of the control system.
PROFINET IO describes a device model, consisting of places
of insertion (slots) and groups of I/O channels (subslots).
The technical characteristics of the field devices are
described by the GSD (General Station Description) on
an XML basis.
PROFINET IO distinguishes between three following device
- IO-Controller: Controller on which the automation
program is run
- IO-Device: remotely assigned field device, which is
assigned to an IO-Controller
- IO-Supervisor: programming device/PC with commissioning
and diagnostics functions
The engineering of PROFINET IO is done in the way familiar
to system integrators from years with PROFIBUS. The decentralized
field buses are assigned to one or more control systems
during configuration. During engineering the IO-Device
is to be configured to the actual system expansion based
on the content in the GSD file. The IO-Device is simultaneously
integrated, appropriately parameterized and configured
into the PROFINET topology (1).
After completion of the engineering process, the installer
loads the data for the expansion into the IO-Controller
(2). The IO-Controller independently takes over data exchange
with the IO-Device (3).
PROFINET CBA is a groundbreaking concept for industrial
automation which fulfills the requirements of plant builders
and operators for an system-wide and manufacturer-spanning
engineering process. The PROFINET component model sees
its real use in distributed automation systems. It is
ideally suited for intelligent field devices with programmable
functionality as well as controllers.
PROFINET CBA is based on the object-oriented modelling
of technological modules. Based on the object model, machines
and installations are structured in PROFINET in the form
of technological modules. The functionality of the technological
modules is encapsulated in uniform PROFINET components.
From the outside, PROFINET components are accessed through
uniformly defined interfaces. They can be arbitrarily
connected in this way.
A distributed automation system designed in this way
allows the modularization of plants and machines and therefore
the reuse of segments of plants and machines. This significantly
reduces engineering costs.
PROFINET based on a component model is described using
a PCD (PROFINET Component Description). It is XML-based
and can be generated either by the Component Generator
of a manufacturer-specific configuration tool.
PROFINET CBA systems. The engineering differentiates
between the programming of the control logic of the individual
technological modules (component generation using manufacturer-specific
configuring tools) and the plant configuration which determines
the communication relationships between the technological
modules (using a PROFINET Connection Editor). As last
engineering step, the connection information and configuration
data are downloaded to the PROFINET components with a
PROFINET specifies a model for the integration of existing
PROFIBUS and other fieldbus systems like INTERBUS and
DeviceNet. This allows the construction of arbitrarily
mixed systems consisting of fieldbus- and Ethernet-based
segments. Thus a smooth technology transition is possible
from fieldbus-based systems to PROFINET.
The large number of existing fieldbus systems makes
it necessary to support their simple integration into
PROFINET for reasons of investment protection. The following
cases are distinguished:
- The system operator would like to be able to integrate
existing installations into a newly installed PROFINET
- The system and machine builder would like to use the
established, documented device lines unchanged for PROFINET
- The device manufacturer would like to be able to integrate
existing field devices into PROFINET installations without
any costs of change.
Fieldbus solutions can easily and seamlessly be connected
into a PROFINET system using proxies. The proxy functions
as a representative of the fieldbus device on the Ethernet.
It integrates the nodes connected to the underlying fieldbus
system into the overlying PROFINET system. This allows
the advantages of fieldbuses like high dynamics, locally
exact diagnostics, and automatic system configuration
to be used in the PROFINET world without settings in the
devices. The transfer of system advantages simplifies
planning due to well-understood workflows and the commissioning
and operation using the complete diagnostic capabilities
of the fieldbus system. Device and software tools are
also supported in the usual manner and integrated into
the management of the PROFINET system.
The proxy concept allows the device manufacturer to
provide a high degree of investment protection to the
plant and machine builder and end user.