Siemens SIMATIC S7-300 CPU Data: CPU 315-T-2 DP - Communication Load

Cycle and response times
7.2 Cycle time
7.2.4 Communication Load
Configured communication load (PG/OP communication)
The CPU operating system continuously provides a specified percentage of total CPU
processing performance (time-sharing technology) for communication tasks. Processing
performance not required for communication is made available to other processes.
In the hardware configuration, you can set the load due to communications between 5% and
50%. Default value is 20%.
You can use the following formula for calculating the cycle time extension factor:
100 / (100 - configured communication load in %)
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Figure 7-3 Breakdown of a time slice
Example: 20% communication load
You have configured a communication load of 20% in the hardware configuration.
The calculated cycle time is 10 ms.
Using the above formula, the cycle time is extended by the factor 1.25.
Example: 50 % communication load
You have configured a communication load of 50 % in the hardware configuration.
The calculated cycle time is 10 ms.
Using the above formula, the cycle time is extended by the factor 2.
S7-300 CPU Data: CPU 315T-2 DP
Manual, 12/2005, A5E00427933-02
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