Siemens SIMATIC S7-400H Manual page 330

Glossary
Synchronization module
An interface module to the redundant link on a fault–tolerant system
TROUBLESHOOTING
An operating mode of the standby CPU of a fault–tolerant system in which the
CPU performs a complete self–test..
Update
In the update system mode of a fault–tolerant system, the master CPU updates
the dynamic data of the standby CPU (synchronization).
Glossary-4
Automation System S7-400H Fault-tolerant Systems
A5E00068197-07