Siemens SIMATIC S7-1500 System Manual page 100

Conditions:
• H-Sync forwarding is not relevant for redundant S7-1500H systems. With the redundant
S7-1500H system, the H-Sync frames are transmitted exclusively via the fiber-optic cables.
• When you use PROFINET devices with more than two ports (e.g. switch) in the
PROFINET ring of an R-system, then H-Sync Forwarding is mandatory for these
devices.
H-Sync frames leave the PROFINET ring with a switch without H-Sync forwarding. This
results in an additional load on the network. Another serious result is that the redundancy
of other R-systems in the network can fail or startup can be prevented.
• H-Sync forwarding is recommended for all devices in the PROFINET ring if you are
using PROFINET devices with only 2 ports in the PROFINET ring of an R-system.
When you operate PROFINET devices without H-Sync forwarding in the PROFINET ring of
the redundant S7-1500R system, the following scenario will result in an additional cycle
time increase:
1.
2.
3.
4.
5.
6.
Figure 5-20
S7-1500R/H redundant system
System Manual, 01/2024, A5E41814787-AF
The redundant S7-1500R system is in the RUN-Redundant system state.
The PROFINET cable which directly connects the two CPUs fails.
The PROFINET ring is interrupted.
The PROFINET ring is being reconfigured.
PROFINET devices without H-Sync forwarding do not forward any H-Sync frames during the
reconfiguration time of the PROFINET ring.
The cycle time increases by the reconfiguration time of the PROFINET ring.
Failure of the PROFINET cable between the CPUs
System overview
5.3 S7-1500 R/H-CPUs
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