Influences On The Cycle Time In Run-Redundant System State - Siemens Simatic S7-1500 Function Manual

5.3.3

Influences on the cycle time in RUN-Redundant system state

RUN-Redundant system state
In RUN-Redundant system state, the primary CPU guides the process. The primary CPU
continuously synchronizes itself with the backup CPU. In the event of a failure of the primary
CPU, the backup CPU adopts its role and thus control over the process.
Cycle time without interruption of the cyclic program
In RUN-Redundant system state, the backup CPU has a time lag compared to the primary
CPU. This time lag results from the time required for event-controlled synchronization of data
from the primary CPU to the backup CPU.
The following figure shows the phases which the CPUs run through without an interruption of
the cyclic program.
①
②
③
④
Figure 5-2
The cycle time
backup CPU compared to the primary CPU. The time lag results from the time required for
the synchronization of the data between primary CPU and backup CPU. The synchronization
between primary CPU and backup CPU occurs automatically if required. The more data has
to be synchronized between the CPUs during a cycle, the greater the time lag. The program
cycle ends as soon as the backup CPU has reached the end of its cyclic program. The
primary CPU starts the next cycle as soon as the backup CPU reports the cycle end to the
primary CPU
Cycle and response times
Function Manual, 10/2018, A5E03461504-AD
5.3 Influences on the cycle time of the S7-1500R/H redundant system
Cycle time
Cycle of the backup CPU
Time lag
Cycle end and start of the next cycle (cycle control point)
Cycle time without interruption of the cyclic program
①
includes the cycle of the backup CPU
④
.
Cycle and response times of the S7-1500R/H redundant system
② ③
and the time lag of the
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