PROFINET
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Real-time communication (RT)
A data communication over the UDP/IP channel is provided with a certain amount of administrative
and control information for addressing and flow control, all of which slows data traffic.
To enable Real-Time capability for cyclical data exchange, PROFINET abandons partially IP address-
ing and flow control over UDP for RT communications. The communication mechanisms of the
Ethernet (Layer 2 of the ISO/OSI model) are very suitable for this. RT communications can always run
in parallel with NRT communications.
The services of PROFINET IO
Cyclic data exchange
For the cyclic exchange of process signals and high-priority alarms, PROFINET IO uses the RT
channel.
Acyclic data exchange (record data)
The reading and writing of information (read/write services) can be performed acyclically by the
user. The following services run acyclically in PROFINET:
–
parameterization of individual submodules during system boot
– reading of diagnostic information
– reading of identification information according to the "Identification and Maintenance (I&M)
functions"
– reading of I/O data
Address assignment
In IP-based communications, all field devices are addressed by an IP address.
PROFINET uses the Discovery and Configuration Protocol (DCP) for IP assignment.
In the delivery state each device amongst others has a MAC address. This information is enough to
assign each field device a unique name (appropriate to the installation).
Address assignment is performed in two steps:
Assignment of a unique plant specific name to the field device.
Assignment of the IP address by the IO-Controller before system boot based on the plant specific
(unique) name.
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