Siemens Simatic S7-1500 Function Manual page 58

Switchover from SYNCUP to RUN-Redundant
The system checks continuously which cycle time would result from a change to the RUN-
Redundant system state. If this cycle time would be ≤ 80% of the maximum cycle time over
multiple cycles, the transition is initiated.
Note
Determination of the cycle time during the SYNCUP
You can track the progress of the SYNCUP on the display of the primary CPU and backup
CPU. At each cycle control point the backup CPU sends a status message on its program
progress to the primary CPU. The display of the primary CPU indicates the duration of the
time lag of the backup CPU.
In addition to viewing the progress in the displays, the progress of the SYNCUP can also be
read out using the "RT_INFO" instruction.
Reasons for cancellation of the SYNCUP
Possible causes for the cancellation of the SYNCUP are:
● The load of the user program or the load on the redundancy connections between
primary and backup CPU is too high
● The maximum cycle time of the primary CPU was exceeded
An overview of all reasons for the cancellation of the SYNCUP and remedial measures is
available in the system manual S7-1500R/H redundant system
(https://support.industry.siemens.com/cs/ww/en/view/109754833).
Disable SYNCUP
To avoid the described effects of the SYNCUP on the cycle times during critical process
states, use the instruction "RH_CTRL".
The "RH_CTRL" instruction can be used to disable the SYNCUP system state for the
S7-1500R/H redundant system. If the disable is no longer required, the "RH_CTRL"
instruction can be used to enable the SYNCUP system state once again.
More information on the "RH_CTRL" instruction is available in the system manual S7-
1500R/H redundant system
(https://support.industry.siemens.com/cs/ww/en/view/109754833).
Cycle and response times
Function Manual, 10/2018, A5E03461504-AD
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
57