Reaction Time - Siemens SIMATIC S7-400 Reference Manual

3.5

Reaction Time

Definition of the Reaction Time
The reaction time is the time from an input signal being detected to changing an
output signal linked to it.
Variation
The actual reaction time is somewhere between a shortest and a longest reaction
time. For configuring your system, you must always reckon with the longest
reaction time.
The shortest and longest reaction times are analyzed below so that you can gain
an impression of the variation of the reaction time.
Factors
The reaction time depends on the cycle time and on the following factors:
• Delay in the inputs and outputs
• Additional DP cycle times on the PROFIBUS-DP network
• Execution of the user program
Delay in the Inputs and Outputs
Depending on the module, you must heed the following time delays:
• For digital inputs:
• For interrupt-capable digital inputs: the input delay +
• For digital outputs:
• For relay outputs:
• For analog inputs:
• For analog outputs:
The time delays can be found in the technical specifications of the signal modules.
Automation System S7-400 CPU Specifications
A5E00165965-01
Cycle and Reaction Times of the S7-400
the input delay
the module-internal preparation time
negligible time delays
typical time delays from 10 to 20 ms.
The delay of the relay outputs depends, among other
things, on the temperature and voltage.
cycle time of analog input module
response time of the analog output module
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