Data Translation DT9824, User Manual, Page: 55 / 102

Principles of Operation
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Figure 16: Digital Output Circuitry
Digital outputs resemble a switch; the switch is closed if the state of the digital output line is 1,
and the switch is open if the state of the digital output line is 0. On power up or reset, the
digital outputs are open.
Channel-to-Channel Isolation
The DT9824 module includes channel-to-channel isolation of up to 250 V between digital I/O
lines. If you require greater channel-to-channel isolation, use every other digital line. This
reduces the number of digital I/O lines, but provides channel-to-channel isolation of 500 V
(one channel can be +250 V while the adjacent channel can be –250 V).
Resolution
The DT9824 module provides a resolution of eight bits for the digital input port to
accommodate the eight isolated digital input lines and a resolution of eight bits for the digital
output port to accommodate the eight isolated digital output lines. These lines are organized
as isolated, dedicated ports. You cannot configure port resolution through software.
Operation Modes
The following digital I/O operation modes are supported for the DT9824 module:
• Single-value operations are the simplest to use but offer the least flexibility and
efficiency. You use software to specify the digital input or output port (the gain is
ignored). Data is then read from or written to the corresponding digital I/O lines.
• Continuous digital input takes full advantage of the capabilities of the DT9824 module
using the analog input clock source, conversion mode, and buffer. The analog input
sample clock then paces acquisition of the analog input channels as well as the digital
input port; refer to
page 50 for more information about specifying the digital input port in
the analog input channel-gain list.