Siemens SIMATIC ET 200AL, System Manual

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Functions
5.5 Real-time communication
PROFINET with STEP 7
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Function Manual, 05/2021, A5E03444486-AL
Time ranges of the communication cycle
The communication cycle is divided into three time ranges, which are shown in the following
chart:
Figure 5-50 Reserving bandwidth
• IRT data (synchronized communication)
This time range can be reserved in specific steps, depending on the send clock. Only IRT
data is transmitted during this time range.
• RT data (real-time communication)
The cyclic RT data is transferred in this time range. RT data is prioritized over "normal"
TCP/IP data. TCP/IP data or Ethernet frames can have a priority of between 1 and 7. RT data
have the Priority 6.
• TCP/IP data (standard communication)
Standard communication (e.g., TCP/IP) is transmitted in the remaining interval of the
communication cycle.
In STEP 7, you can set the ratio of the bandwidth usage of cyclic IO data to standard
communication. For information on how to set the bandwidth usage, refer to the section
Setting the bandwidth usage for the send clock (Page 1)