Analog Modules
4-133
Programmable Logic Controllers S7-300 Module Data
A5E00105505-03
”Software filter 8 channels” mode
In “Software filter 8 channels” mode, the analog/digital conversion occurs in exactly
the same way as in “hardware filter 8 channels” mode. That is to say, as the
module contains four analog/digital converters (ADC), all four of the ADCs convert
simultaneously for channels 0, 2, 4 and 6. Once the even-numbered channels are
converted, all the ADCs convert simultaneously for the odd-numbered channels 1,
3, 5 and 7 (see Figure 4-43).
Scan time
Start analog conversion
(simultaneous)
K0 K2 K4 K6
K1 K3 K5 K7
Start analog conversion
(simultaneous)
Figure 4-43 Software filter 8 channels scan time
Scan time of the module
The channel conversion time depends, however, on the programmed interference
frequency suppression. When you set an interference frequency of 50 Hz, the
channel conversion time including communication time is 30 ms. When you set an
interference frequency of 60 Hz, the channel conversion time is 25 ms. When you
set an interference frequency of 400 Hz, the channel conversion time is reduced to
8 ms. As with 8-channel hardware filter mode, the module must be switched over
by means of opto MOS relays with a time of 12 ms for switching to the other
channel of the group. This relationship is shown in the table that follows.
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