Siemens SIMATIC S7-400H System Manual page 280

S7-400 cycle and reaction times
16.7 Examples of calculating the cycle and reaction times
Calculating the longest reaction time
● Longest reaction time
● Delay of inputs and outputs
● All the components are installed in the central unit, so DP cycle times can be ignored.
● Use case 1: The system sets a digital output channel after a digital input signal is read in.
● Use case 2: The system reads in and outputs an analog value. The result is a reaction
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23.2 ms * 2 = 46.4 ms.
– The maximum input delay of the digital input module SM 421; DI 32xDC 24 V is 4.8 ms
per channel
– The output delay of the digital output module SM 422; DO 16xDC 24 V/2A is negligible.
– Analog input module SM 431; AI 8x13 bits was configured for 50 Hz interference
frequency suppression. This results in a conversion time of 25 ms per channel. As
eight channels are active, a cycle time of the analog output module of 200 ms results.
– Analog output module SM 432; AO 8x13 bits is configured for operation in the
measuring range 0 ...10V. This results in a conversion time of 0.3 ms per channel. As
eight channels are active, a cycle time of 2.4 ms results. The transient time of a
resistive load of 0.1 ms must be added to this. The result is an analog output response
time of 2.5 ms.
The result is a reaction time of:
Reaction time = 46.4 ms + 4.8 ms = 51.2 ms
time of:
Reaction time = 46.4 ms + 200 ms + 2.5 ms = 248.9 ms
System Manual, 09/2007, A5E00267695-03
S7-400H