Functions
5.6 PROFINET with performance upgrade
PROFINET with STEP 7 V15
Function Manual, 12/2017, A5E03444486-AH
195
Setting low send clocks (example CPU 1518-4 PN/DP)
Requirement: The "Make 'high performance' possible" option is enabled.
1. Select the PROFINET IO system in the network view of STEP 7.
2. In the Inspector window, go to "Properties" > "General" > "PROFINET" > "Domain
management" > "Sync domains" > "Name of the sync domain".
3. Select the send clock for "Send clock" in the drop-down list.
Figure 5-61 Setting low send clocks
Requirements for the fragmentation process (example CPU 1518-4 PN/DP)
If you use the following combinations for send clock and bandwidth settings, the devices in
the IO system use the fragmentation process.
● Send clock cycle 125 µs: Always fragmentation irrespective of the bandwidth setting.
● Send clock cycle 187.5 µs: Fragmentation with the bandwidth settings "Maximum 50%
cyclic IO data. Balanced proportion." and "Maximum 90% cyclic IO data. Focus on cyclic
IO data."
The PROFINET IO interface of the controller supports fragmentation if all the ports except
one are deactivated.
Optimizing port settings for low send clocks
You can further optimize the bandwidth use in your PROFINET IO system by using cables
with a short cable length (< 20 m) or a short signal delay (max. 0.12 µs) between the
devices.
To configure cables with a shorter length or signal delay in STEP 7, follow these steps:
1. Select the port in the topology view of STEP 7.
2. Navigate in the Inspector window to "Port interconnection" in the "Partner port" box.
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