Siemens SIMATIC Manual page 393

Cycle time of module in 8-channel mode (software filter)
The channel conversion time is based on the programmed interference frequency. The
channel conversion time is 32 ms, including communication time, when you set an
interference frequency of 50 Hz. The channel conversion time is 27 ms when you set an
interference frequency of 60 Hz. You can reduce channel conversion times to 9 ms by
setting an interference frequency of 400 Hz. As in "hardware filter, 8channel" mode, the
module has to toggle to the second channel of the group within a changeover time of 16 ms
using the Opto-MOS relays. The table below shows this correlation.
Table 6- 26
Interference frequency
50 Hz
60 Hz
400 Hz
* Channel cycle time = channel conversion time + 12 ms channel changeover time within the group
4-channel mode (hardware filter)
In this mode, the module does not change between the channels of the groups. The four
ADCs of the module simultaneously convert the channels 0, 2, 4 and 6.
Figure 6-25
Cycle time of the module in 4-channel mode (hardware filter)
The converted value settles to 100% within 80 ms and is updated at intervals of 10 ms when
4-channel mode is set. The channel and module cycle times are always identical, as the
module does not change between the channels of a group: 10 ms.
Channel conversion time = channel cycle time = module cycle time = 10 ms
S7-300 Module data
Manual, 06/2017, A5E00105505-AJ
6.9 Analog input module SM 331; AI 8 x RTD; (6ES7331-7PF01-0AB0)
Cycle times in "8-channel mode (software filter)"
4-channel mode cycle time (hardware filter)
Channel cycle time*
48 ms
43 ms
25 ms
Analog modules
Module cycle time (all channels)
96 ms
86 ms
50 ms
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