Siemens SIMATIC S7-400H System Manual page 274

S7-400 cycle and reaction times
16.5 Reaction time
Longest reaction time
The figure below shows the conditions under which the longest reaction time is reached.
Figure 16-9
Calculation
The (longest) reaction time is made up as follows:
● 2 × process image transfer time of the inputs +
● 2 × process image transfer time of the outputs +
● 2 x operating system processing time +
● 2 x program processing time +
● 2 x delay of the DP slave frame (including processing in the DP master) +
● Delay at the inputs and outputs
This is equivalent to the sum of twice the cycle time and the delay in the inputs and outputs
plus twice the DP cycle time.
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Longest reaction time
System Manual, 09/2007, A5E00267695-03
S7-400H