Siemens SIMATIC ET 200AL System Manual page 1124

Time ranges of the communication cycle
The communication cycle is divided into three time ranges, which are shown in the following
chart:
Figure 5-45
●
This time range can be reserved in specific steps, depending on the send clock. Only
IRT data is transmitted during this time range.
●
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.
●
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 181)
PROFINET with STEP 7 V15
Function Manual, 12/2017, A5E03444486-AH
Reserving bandwidth
IRT data (synchronized communication)
RT data (real-time communication)
TCP/IP data (standard communication)
Functions
5.5 Real-time communication
177