Analog Input Subsystem
C-11
Analog Input Multiplexer
The EXP-1800 Input Multiplexers can expand the number of physical
channels to 256 single-ended analog input channels. The DAS-1800
hardware automatically switches the multiplexer channels. This feature
allows acquisition from the multiplexer channels in DMA mode.
To enable DriverLINX to use multiplexer(s), select the “16 SE” option for
Analog Input Channels in the Device Configuration dialog box. Then
enter the number of EXP-1800s in the Special Device Settings dialog.
With this configuration, DriverLINX treats the DAS-1800 as having a
possible 272 Logical Channels, instead of 16, analog input channels.
Channels 0 - 15 refer to the native analog input channels on the
DAS-1800 while channels 16 - 271 address one of the 256 mux channels.
While a DAS-1800 with 16 external multiplexers has 272 logical
channels, it still has only 256 physical channels. Each mux supports 16
channels and the hardware electronically switches the 16 mux inputs to
the one physical channel on the DAS-1800 where you attached the mux.
Therefore, addressing a native channel (0-15), which has a mux attached,
is logically equivalent to directly addressing the lowest numbered channel
on the attached mux.
DriverLINX uses a static addressing scheme for attaching multiplexers.
Removing an input from one native channel and attaching a mux to that
input channel does not change the logical addresses of any other input
channel. Also, if you reattach the input you removed from the native
channel to the first mux channel, existing software can still read that input
at its original logical address.
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