Chapter 4
Digital I/O Functionality
NI CVS-1450 Series User Manual
4-4
ni.com
For more information about creating a timed pulse output, refer to the
TTL Input 0, TTL Input 1, TRIG 0, and ISO Input 8 can alternatively
function as general purpose inputs. ISO input 5 can alternatively function
as a latch input for the product selection port.
Timed Pulse Output
The CVS-1450 device is capable of timed pulse output on six different
digital outputs, which provides precise control over time-critical signals,
such as camera exposure. This section describes the various uses for the
timed pulse output and the parameters you can set to control these outputs.
Uses for timed pulse output include controlling camera reset and exposure,
controlling strobe lighting, operating plungers on an assembly line, and
communicating with PLCs. You can configure the start of the pulse output
generation to occur from software or from a
rising
or
falling edge
of a
trigger input.
In addition to controlling the timing of pulse output, you can also configure
the polarity of the output signal, resulting in a high-true or low-true signal.
Based on the polarity setting, the output signal asserts after the appropriate
delay time and de-asserts after the configured pulse width. You can set the
delay time in microseconds or in quadrature encoder counts from the start
signal—either a hardware trigger or a software command. Width is always
configured in microseconds.
Initiating a Timed Pulse
Each timed pulse generator has a trigger input that specifies whether to wait
on a particular trigger input to generate the pulse or to immediately
generate the pulse when software sets the pulse mode to
Start
.
When the pulse generator is configured for a particular trigger input, after
generating a pulse, it waits for another trigger before generating another
pulse. When the pulse generator is configured to immediately generate the
pulse on a software start, after generating a pulse, it immediately generates
another pulse.
If the trigger input is set to
Immediate
, the pulse generation occurs as soon
as the pulse mode is set to
Start
. If the trigger input is set to one of the
hardware trigger inputs, the timed pulse output waits for an assertion edge
on the appropriate trigger input. The assertion edge is configurable based
on the trigger polarity parameter. It then generates one pulse and rearms to
