S7-400 cycle and response times
19.7 Examples of calculating the cycle and response times
S7-400H
378 System Manual, 03/2012, A5E00267695-11
Calculating the longest response time
● Longest response time
22.5 ms * 2 = 45 ms.
● Delay of inputs and outputs
– The maximum input delay of the digital input module SM 421; DI 32×DC 24 V is
4.8 ms per channel
– The output delay of the digital output module SM 422; DO 16×DC 24 V/2A is
negligible.
– Analog input module SM 431; AI 8×13Bit was parameterized for 50 Hz interference
frequency suppression. The result is a conversion time of 25 ms per channel. As
8 channels are active, a cycle time of the analog input module of 200 ms results.
– Analog output module SM 432; AO 8×13Bit was parameterized for operation in the
measuring range 0 ... 10 V. This results in a conversion time of 0.3 ms per channel.
Since 8 channels are active, the result is a cycle time of 2.4 ms. 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.
● All components are installed in the central unit, so DP cycle times can be ignored.
● Case 1: The system sets an output channel of the digital output module after a digital
input signal is read in. The result is as follows:
Response time = 45 ms + 4.8 ms = 49.8 ms.
● Case 2: The system reads in and outputs an analog value. The result is as follows:
Response time = 45 ms + 200 ms + 2.5 ms = 247.5 ms.
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