System overview
5.3 S7-1500 R/H-CPUs
S7-1500R/H redundant system
System Manual, 01/2024, A5E41814787-AF
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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:
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.
5. 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.
Figure 5-20 Failure of the PROFINET cable between the CPUs
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