Data Translation DT9800 Series, User Manual

Page: 57 / 162

Principles of Operation
45
2
2
2
2
2
2
2
2
2
Resolution
The resolution of the digital input port is fixed at 8 bits; the resolution
of the digital output port is also fixed at 8 bits.
You cannot program the digital I/O resolution in software.
Operation Modes
The DT9800 Series function 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 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 input takes full advantage of the capabilities
of the DT9800 Series function modules. In this mode, enter all
eight digital input lines of Port A as channel 16 of the analog
input channel-gain list; program this mode through the A/D
subsystem. Using this mode, you can specify a clock source, scan
mode, trigger source, buffer, and buffer wrap mode for the digital
input operation. Refer to
page 16 for more information on
specifying digital input lines for a continuous digital input
operation.
• Dynamic digital output is useful for synchronizing and
controlling external equipment and allows you to output data to
the dynamic digital output line each time an analog input value
is acquired. This mode is programmed through the A/D
subsystem; refer to
page 17 for more information.