Triggers

A trigger is an input signal received by an instrument or instrument channel that causes the instrument or channel to perform an action. Triggers are routed to input terminals to coordinate actions.

An input terminal is a physical trigger line, such as a PXI trigger line, or an output terminal on another instrument or channel, where an instrument or channel awaits a digital edge trigger signal.

For purposes of programming instruments with NI APIs, triggers comprise two parts:

• The action, represented with the name of the trigger, that you want the instrument or channel to take.
• The signal condition you want to serve as the stimulus for that action (for example, a rising or falling digital edge on a signal, or a software-generated edge you configure).

Triggers can be internal (software-generated) or external. You can export external triggers and use them with events to synchronize hardware operation with external circuitry or other instruments.

NI RF instruments accept external triggers routed between the instruments using PXI trigger lines. Events assigned to a PXI trigger line can coordinate actions across channels and across instruments.

Events

An event is a signal generated by an instrument or instrument channel that signifies a state change of the instrument, the arrival of a certain kind of sample, the production of a certain amount of samples, or the passage of time. Events can be routed to output terminals to coordinate the action of multiple channels or multiple instruments.

Triggers and clocks are generally considered input signals. Exportable triggers and clocks, such as the Sample Clock, can also be considered output signals. Output signals that do not have a trigger or clock counterpart are called events.

You typically configure events for a specific hardware condition and then export those events for use in the test program or export them to a PXI trigger line to cause an action in another instrument configured to wait for a trigger on the same PXI trigger line.