Siemens SIMATIC Manual page 408

Analog modules
6.10 Analog input module SM 331; AI 8 x TC; (6ES7331-7PF11-0AB0)
Cycle time of the module in 8-channel mode (hardware filter)
The channel conversion time, including module communication time, is 91 ms. The module
must change to the second channel of the group using OptoMOS relays when conversion is
completed. Opto-MOS relays require 7 ms for switching and settling. Each channel requires
a time of 98 ms, i.e. the total cycle time equals 196 ms.
Cycle time = (t
Cycle time = (91 ms + 7 ms) x 2
Cycle time = 196 ms
t : Conversion time for one channel
C
t : Time for changing over to the other channel in a channel group
C
8-channel mode (software filter)
Analog-to-digital conversion in this mode is similar to conversion in 8-channel mode
(hardware filter). The four ADCs of the module simultaneously convert channels 0, 2, 4 and
6. The ADCs first convert the channels with even numbers, and then the channels with the
odd numbers 1, 3, 5 and 7 (see the figure below.)
Figure 6-30
408
+ t ) x 2
K U
8-channel mode cycle time (software filter)
S7-300 Module data
Manual, 06/2017, A5E00105505-AJ