Data Translation DT9834 Series, User Manual

Page: 95 / 186

Principles of Operation
95
Digital I/O Features
This section describes the following features of digital I/O operations:
• Digital I/O lines, described below
• Operation modes, described on page 95
Digital I/O Lines
DT9834 Series modules support one digital input port, consisting of 16 digital input lines
(lines 0 to 15) and one digital output port, consisting of 16 digital output lines (lines 0 to 15).
The resolution is fixed at 16-bits.
You can specify the digital I/O line that you want to read or write in a single-value digital I/O
operation. Refer to
page 95 for more information about single-value operations.
In addition, you can specify the entire digital input port in an analog input channel list to
perform a continuous digital input operation, or you can specify the entire digital output port
in an output channel list to perform a continuous digital output operation. Refer to
page 95 for
more information about continuous digital I/O operations.
A digital line is high if its value is 1; a digital line is low if its value is 0. On power up or reset,
a low value (0) is output from each of the digital output lines.
The DT9834 Series modules allow you to program the first eight digital input lines to perform
interrupt-on-change operations. Refer to
page 96 for more information.
The DT9834 Series modules provide a dynamic digital output line that you can update
whenever an analog input channel is read. The dynamic digital output line is in addition to
the 16 digital output lines. Refer to
page 96 for more information.
Operation Modes
The DT9834 Series modules support the following digital I/O operation modes:
• Single-value operations are the simplest to use but offer the least flexibility and efficiency.
You use software to specify the digital I/O port and a gain of 1 (the gain is ignored). Data
is then read from or written to all the digital I/O lines. For a single-value operation, you
cannot specify a clock or trigger source.
Single-value operations stop automatically when finished; you cannot stop a single-value
operation.
• Continuous digital I/O takes full advantage of the capabilities of the DT9834 Series
modules. You can specify a clock source, scan mode, trigger source, buffer, and buffer
wrap mode for the operation.
−
Digital input – For digital input operations, enter the digital input port (all 16 digital
input lines) as channel 16 or 32 in the analog input channel list; refer to page 80 for
more information. The input sample clock (internal or external) paces the reading of
the digital input port (as well as the acquisition of the analog input and counter/timer
channels); refer to
page 84 for more information.