Data Translation DT9834 Series, Руководство пользователя

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Chapter 5
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Specifying the Digital Input Port in the Analog Input Channel List
The DT9834 Series modules allow you to read the digital input port (all 16 digital input lines)
using the analog input channel list. This feature is particularly useful when you want to
correlate the timing of analog and digital events.
To read the digital input port, specify channel 16 or channel 32 in the analog input channel list.
Use channel 16 for modules with 16 single-ended channels or eight differential channels; use
channel 32 for modules with 32 single-ended channels or 16 differential channels. You can
enter channel 16 or 32 anywhere in the list, and you can enter it more than once, if desired.
The digital input port is treated like any other channel in the analog input channel list;
therefore, all the clocking, triggering, and conversion modes supported for analog input
channels are supported for the digital input port, if you specify them this way.
Maximum Rate
The maximum rate at which the module can read the digital input port depends on the total
number of analog input channels (see
page 79 ) and counter/timer channels (see the next
section) in the channel list.
For example, since the maximum throughput of the analog input subsystem is 500
kSamples/s, the module can read one analog input channel and the digital input port (two
channels/ports) at a rate of 250 kSamples/s each or three analog input channels and the
digital input port (four channels/ports) at a rate of 125 kSamples/s each.
Specifying Counter/Timers in the Analog Input Channel List
On the DT9834 Series modules, you can read the value of one or more of the five
counter/timer channels using the analog input channel list. This feature is particularly useful
when you want to correlate the timing of analog and counter/timer events.
To read a counter/timer channel, specify the appropriate channel number in the analog input
channel list (refer to
Table 8 on page 81 ). You can enter a channel number anywhere in the list,
and you can enter it more than once, if desired.
You need two channel list entries to read one 32-bit counter value. The first entry stores the
lower 16-bit word, and the second entry stores the upper 16-bit word. If you need only the
lower 16-bit word, you do not have to include the second entry. The entire 32-bit count value is
latched when the lower 16-bit word is stored. This prevents the counter/timer value that is
being read from changing between samples.
Table 8 lists the channel number(s) to use for each counter/timer.