Siemens Simatic S7-300 Specifications download pdf (Page 78)

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S7-300 Automation System CPU Specifications: CPU 31xC and CPU 31x

5-18 A5E00105475-03

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Table 5-10 Calculating the response time

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- Multiply the physical cycle time by factor 2.

Now add I/O delay. Now add the I/O delay and the DP cycle

times of the PROFIBUS-DP network.

The result is the shortest response time. The result is the longest response time.

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The interrupt response time is the time that expires between the first occurrence of

an interrupt signal and the call of the first interrupt OB instruction. The following

rule generally applies: Higher-priority interrupts are executed first. This means that

the interrupt response time is increased by the program processing time of the

higher-priority interrupt OBs and the interrupt OBs of equal priority which have not

yet been executed (queued).

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The formula below show how you can calculate the minimum and maximum

interrupt response times.

Table 5-11 Process and diagnostic interrupt response times

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Minimum interrupt reaction time of the

CPU

+ Minimum interrupt reaction time of the

signal modules

+ DP cycle time on the PROFIBUS DP

= Quickest interrupt reaction time

Maximum interrupt reaction time of the CPU

+ Maximum interrupt reaction time of the signal

modules

+ 2 x DP cycle time on the PROFIBUS DP

The maximum interrupt reaction time is longer

when the communication functions are active.

The extra time is calculated with the following

formula:

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Substantial longer time is possible when n =

longer cycle due communication

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Siemens Simatic S7-300 Specifications Page 78