Siemens Simatic S7-300 - Page 331

Analog modules
6.10 Analog input module SM 331; AI 8 x TC; (6ES7331-7PF11-0AB0)
S7-300 Automation System Module data
Manual, 08/2006, A5E00105505-04
6-97
Cycle time of module in 8-channel mode (hardware filter)
The channel conversion time, including module communication time, is 91 ms. After this
cycle, the module has to change over to the second channel of the group using OptoMOS
relays. Opto-MOS relays require switching and settling times of 7 ms. Each channel requires
a time of 98 ms, i.e. the total cycle time equals 196 ms.
Cycle time = (t
K
+ t
U
) x 2
Cycle time = (91 ms + 7 ms) x 2
Cycle time = 196 ms
t
C
: Conversion time for one channel
t
C
: Time for changing over to the other channel in a channel group
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 analog-to-digital converters (ADC) of the module simultaneously
convert channels 0, 2, 4 and 6. The ADCs first convert the channels with even numbers,
then those with the odd numbers 1, 3, 5 and 7 (see the figure below.)
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Figure 6-30 8-channel mode cycle time (software filter)