Rockwell Automation 1746-NI16V SLC 500 Analog Input Modules User Manual - Manual (Page 52)

Publication 1746-UM001A-US-P
5-4 Channel Configuration, Data, and Status
Select Channel Enable (Bit 15)
Determine which channels are used in your program and enable
them. Place a 1 in bit 15 to enable a channel. Place a 0 in bit 15 to
disable the channel. In class 1, only the handshake bit (bit 2) needs to
be set to transmit this configuration bit change.
The 1746-NI16 only samples data from channels that are enabled. To
optimize module operation and minimize throughput times, disable
unused channels by setting the channel enable bit to 0.
When the channel enable bit is set (1), the module reads the
configuration word information you have selected. While the enable
bit is set, modification of the configuration word may lengthen the
module update time for one cycle. If any change is made to the
configuration word, the change must be reflected in the status word
before new data is valid.
While the channel enable bit is cleared (0), the channel data word and
status word values are cleared. After the channel enable bit is set (1),
the channel data word and status word remain cleared until the
module sets the channel status bits (bits 15, 14, and 13 to 1, 1, and 1)
in the channel status word, signifying that the channel is operating
without an error. See “Channel Status Checking” on page 5-16.
Select Channel Filter Frequency (Bits 14 through 12)
The 1746-NI16 module features eight different filter frequencies.
Choose the desired filter by entering the 3-digit binary code in bits 12
through 14 of the channel configuration word. You can select a
different filter setting for each A/D chip. Each chip samples a group of
4 input channels. The groups of A/D inputs are shown in the table on
page 5-5.
The filter selection for all of the channels in a group is selected using
the configuration word of the first channel in each group. These
channels are channels 0, 4, 8, and 12. Even if the first channel in each
group is disabled, the desired filter frequency must be selected in that
channel’s configuration word; otherwise, the default filter frequency of
6Hz is used. Setting the filter frequency in the other channels (1 to 3, 5
to 7, 9 to 11, or 13 to 15) will not select a filter. Instead, the default
filter is selected.
The default filter setting is 6 Hz. The default filter setting is the bit
pattern (0, 0, 0) in bits 14 through 12.