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In DriverLINX, Timing Events specify how the hardware paces or clocks
the sample output. DriverLINX uses the Timing Event to program when
the DDA-08/16 writes the next analog output sample to the DACs.
The DDA-08/16 supports the following Timing Events:
●
None
—
Output requires no
pacing
as DriverLINX is writing only a
single value.
●
Rate
—
The DDA-08/16 supports only fixed rate analog output using
internal and external clocks. The Rate Generator provides a fixed rate
clock with equal time intervals between tics. An internally clocked
Rate Generator produces a fixed rate clock with equal time intervals
between tics. An externally clocked Rate Generator produces a rate
clock with unknown time intervals between tics.
●
Digital
—
DriverLINX uses an external digital input signal to pace
the output to each sample.
Hardware Trigger
You can enable a hardware trigger through software. A hardware trigger is
an externally applied, edge-sensitive, digital signal that determines when
the analog output channels on the quad DACs in the update group can
respond to either an internal or an external pacer clock.
You connect the digital trigger signal to the TRIGGER IN pin (pin 2) of
the main I/O connector. If the trigger is enabled, the board waits for an
active edge on TRIGGER IN. The active edge is software-selectable; at
power-up, the board assumes that the active edge for a hardware trigger is
a falling edge.
When the board detects an active edge, the channels respond to each pulse
of the pacer clock until the trigger circuitry is disabled.
The actual point at which the channels are updated depends on whether
you are using an internal pacer clock or an external pacer clock. These
considerations are described as follows:
●
Internal pacer clock
—
The internal pacer clock remains idle until
the trigger event occurs. When the trigger event occurs, the pacer
clock counter is loaded and the channels are updated. (Note that a
slight time delay occurs between the time the pacer clock counter is
loaded and the time the channels are updated.)
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