User`s guide

Event Types
8-7
Event Callback Property Description
When a timer event occurs, the toolbox executes the
function specified by the TimerFcn property.
Trigger TriggerFcn The toolbox generates a trigger event when a trigger
executes. The video input object executes immediate
triggers. You execute manual triggers by calling
the trigger function. The image acquisition device
executes hardware triggers when a specified condition
is met.
When a trigger event occurs, the toolbox executes the
function specified by the TriggerFcn property.