Siemens SIMATIC Manual page 392

Analog modules
6.9 Analog input module SM 331; AI 8 x RTD; (6ES7331-7PF01-0AB0)
Cycle time of module in 8-channel mode
The channel conversion time, including module communication time, is 84 ms. The module
must change to the second channel of the group using OptoMOS relays when conversion is
completed. Opto-MOS relays require 12 ms for switching and settling. Each channel requires
a time of 97 ms, i.e. the total cycle time equals 194 ms.
Cycle time = (t
Cycle time = (84 ms + 16 ms) x 2
Cycle time = 200 ms
t : Conversion time for one channel
C
t : Channel changeover time within the channel group
C
8-channel mode (software filter)
Analog-to-digital conversion in this mode is identical to the 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 6-24
392
+ t ) x 2
K U
8-channel mode cycle time (software filter)
S7-300 Module data
Manual, 06/2017, A5E00105505-AJ