Siemens CPU 412-5H Equipment Manual page 13

Diagnostics behavior of the synchronization link
S7-400H system V6 with a loaded "Spare part" V4.5 configuration
If there is reduced performance of the redundancy link between the CPUs, the operating
system of the CPU calls the OB 84. The "reduced performance of the redundancy link" event
with configuration as V4.5 corresponds to the "Functional error of the network component"
event with configuration as V6.0.
S7-400H system V6 or higher, with corresponding configuration
If there is reduced performance of the redundancy link between the CPUs in redundant
operation, the operating system of the CPU calls the OB 82. In this case, you can determine the
cause via the detail diagnostics with SFB52 or SFB54.
Note
In redundant operation, the OB 82 is also called on power off/on of a partial system or during
a firmware update of the partner CPU. This is not a problem with the synchronization link but
is instead because the synchronization modules are not emitting any light at this moment.
Diagnostics with STEP 7 / HW Config
You can find the cause of the reduced performance of the redundancy link in the "Sync module
diagnostics" tab in HW Config > Target system > Module information.
For the selected synchronization module, you can display here the following channel-specific
diagnostics data:
Property
Overtemperature
Fiber-optic error
Violation of lower limit
Violation of upper limit
Functional error of the network
component
Failure of a synchronization component
In solo operation, the error ID 0x3592 indicates an error in "a synchronization component". This
error has no effect on the functionality of the CPU in solo operation. However, redundant
operation is no longer possible. To replace the CPU itself in solo operation, perform a master
replacement with the function "Switch to CPU in Rack ... via only one intact redundancy link".
Synchronization modules for S7-400H
Equipment Manual, 04/2020, A5E50072434-AA
4.2 Synchronization modules for S7–400H
Reason
The synchronization module is too hot.
The synchronization module has reached the end of its service life.
The sent or received optical performance is low or too low.
The sent or received optical performance is high or too high.
The quality of the redundancy link between the CPUs
(transmission distance including synchronization modules and fiber-
optic cables) is reduced so that transmission errors are occurring
frequently.
Description of the device
13