S7-400 cycle and response times
19.4 Communication load
S7-400H
366
System Manual, 03/2012, A5E00267695-11
19.4
Communication load
The operating system provides the CPU continuously with the configured time slices as a
percentage of the overall CPU processing resources (time slice technique). Processing
performance not required for communication is made available to other processes.
In the hardware configuration you can specify a communication load value between 5% and
50%. The default value is 20%.
This percentage is to be interpreted as mean value, i.e. communication resources may take
significantly more than 20% of a time slice. The communication portion is then only a few %
or 0% in the next time slice.
The formula below describes the influence of communication load on the cycle time:
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Figure 19-4 Formula: Influence of communication load
Data consistency
The user program is interrupted to process communications. This interruption can be
triggered after any statement. These communication jobs may lead to a change in user data.
As a result, data consistency cannot be ensured over several accesses.
How to ensure data consistency in operations comprising more than one command is
described in the "Consistent data" section.
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Figure 19-5 Distribution of a time slice
The operating system takes a certain portion of the remaining time slice for internal tasks.
This portion is included in the factor defined in the tables starting at 16-3.
Содержание SIMATIC S7-400H
Страница 24: ...Preface 1 1 Preface S7 400H 24 System Manual 03 2012 A5E00267695 11 ...
Страница 46: ...Getting Started 4 5 Special layout features of SIMATIC Manager S7 400H 46 System Manual 03 2012 A5E00267695 11 ...
Страница 120: ...Memory concept 10 1 Overview of the memory concept of S7 400H CPUs S7 400H 120 System Manual 03 2012 A5E00267695 11 ...
Страница 258: ...Communication 14 8 General issues regarding communication S7 400H 258 System Manual 03 2012 A5E00267695 11 ...
Страница 354: ...Synchronization modules 18 3 Selecting fiber optic cables S7 400H 354 System Manual 03 2012 A5E00267695 11 ...
Страница 434: ...Technical data 20 6 Runtimes of the FCs and FBs for redundant I Os S7 400H 434 System Manual 03 2012 A5E00267695 11 ...
Страница 460: ...Function modules and communication processors supported by the S7 400H S7 400H 460 System Manual 03 2012 A5E00267695 11 ...