Siemens Simatic S7-1500 Function Manual page 57

Cycle and response times of the S7-1500R/H redundant system
5.3 Influences on the cycle time of the S7-1500R/H redundant system
In SYNCUP system state, all relevant data is synchronized from the primary CPU to the
backup CPU. At the end of SYNCUP, the backup CPU makes up the time lag to the primary
CPU caused by the synchronization.
SYNCUP system state
• The synchronization of data, in particular the snapshot of the work memory contents,
• During SYNCUP, hardware interrupts are processed with a very significant delay.
• The cycle time increases greatly during the transition from SYNCUP system state to
Therefore, only execute the SYNCUP during uncritical process states.
①
Synchronization of data from the primary CPU to the backup CPU
During this phase all relevant contents of the load memory, work memory, and system
memory of the primary CPU are synchronized to the backup CPU.
②
Copying the load memory and terminating the asynchronous instructions
The primary CPU copies parts of its load memory from its SIMATIC memory card to the
SIMATIC memory card of the backup CPU. The backup CPU restarts and automatically
switches to SYNCUP operating state. The backup CPU copies the transferred load memory
contents to its work memory. Data blocks, process image, etc. are immediately overwritten
with current data from the primary CPU.
③
Snapshot of the work memory contents
The primary CPU saves a consistent snapshot of its work memory contents at the next cycle
control point.
④
Transfer of work memory contents to the backup CPU
During this phase the consistent snapshot is transferred from the primary CPU to the backup
CPU. The transfer of the work memory contents extends the cycle time. The time required
for the transfer of the work memory contents depends on the performance capability of the
CPU and the amount of work memory data.
⑤
Backup CPU makes up the time lag to the primary CPU
During this phase the backup CPU makes up the time lag in program execution to the
primary CPU. As in redundant mode, events are already synchronized during this phase as
needed.
Note
No switchover possible during SYNCUP
If a fault occurs in the primary CPU during SYNCUP, no switchover to the backup CPU is
possible. The SYNCUP is canceled and the backup CPU returns to STOP operating state.
56
CAUTION
extends the cycle time. In addition, no test and commissioning functions can be carried
out during the SYNCUP.
RUN-Redundant.
Cycle and response times
Function Manual, 10/2018, A5E03461504-AD