Analog Modules
4-82
Programmable Logic Controllers S7-300 Module Data
A5E00105505-03
Channel groups
The channels of the SM 331; AI 8 x 16 bits are arranged in four groups of two. You
can only ever assign parameters to one channel group.
The table below shows which channels are parameterized as a channel group in
each case. You will need the channel group number to set the parameters in the
user program with an SFC.
Table 4-51 Assignment of Channels of the SM 331; AI 8 x 16 bits to Channel Groups
Channels ...
... form one Channel Group each
Channel 0
Channel 1
Channel 2
Channel 3
Channel 4
Channel 5
Channel 6
Channel 7
High Speed Update Mode
In the high speed update mode, updates for the two channels in the group occur
three times faster than with multiple channel groups enabled.
Example: If channels 0 and 1 are enabled with 2.5 ms filtering, data updates for
both channels will be available to the PLC every 10 msec. (For other filter settings,
the filter setting equals the update rate.)
The high speed update mode is only available when both channels are enabled on
channel group 0 or 1, in other words, the “measuring method” parameter is set.
However, only channel group 0 or only channel 1 (in other words, not both
together) must be enabled.
Special characteristic of channel groups for hardware interrupts
You can set hardware interrupts in STEP 7 for the channel groups 0 and 1. Note,
however, that a hardware interrupt is set only for the first channel in the channel
group in each case – in other words, for channel 0 or channel 2
Diagnostics
You will find the diagnostic messages that are grouped under the “group diagnosis”
parameter in Table 4-46, on page 4-72.
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