Operating instructions

Communication
6.5 Communication via PROFINET
Control Units CU240S
Operating Instructions, 10/2007, A5E00766042B AC
167
6.5.1 Real-Time (RT) Communication
Real-time communication
If supervisors are involved in communication, this can result in excessively long runtimes for
the production automation system. When communicating time-critical IO use data,
PROFINET therefore uses its own real time channel, rather than TCP/IP.
Definition: Real Time (RT) and determinism
Real time means that a system processes external events over a defined period.
Determinism means that a system responds in a predictable manner (deterministically).
In industrial networks, both of these requirements are important. PROFINET meets these
requirements. PROFINET is implemented as a deterministic real time network as follows:
● Transmission of time-critical data takes place at guaranteed time intervals. To achieve
this, PROFINET provides an optimized communication channel for real time
communication: Real Time (RT).
● An exact prediction of the time at which the data transfer takes place is possible.
● Problem-free communication using other standard protocols is guaranteed within the
same network.
6.5.2 Addresses
MAC address
Each PROFINET device is assigned a worldwide unique device identifier in the factory. This
6-byte long device identifier is the MAC address. You can see the MAC address with support
of commissioning tools as PST, STEP 7 or STARTER. The MAC address is divided up as
follows:
● 3 bytes manufacturer's ID and
● 3 bytes device identifier (consecutive number).
The MAC address is indicated on the rating plate of the Control Unit. The MAC address is
stored in the parameter r61002.
Example for a MAC address: 08-00-06-6B-80-C0
IP address
The IP address is unique within the network. A PROFINET device also requires an IP
address to be addressed as a node on Industrial Ethernet. The IP address is made up of 4
decimal numbers with a range of values from 0 through 255. The digit blocks are separated
by points, e g. 192.188.1.1. The IP address is made up of the following:
● The address of the (sub-) network
● The address of the node (generally called the host or network node)