EAGLE has a synchronous trigger input to control image acquisition dependent on external events. The trigger input is TTL controlled and the flank (high-low, low-high), which causes a trigger event, can be chosen by function is_SetExternalTrigger(). The trigger pulse width must at least amount to 20 ms.
Pre-trigger mode

Fig. 40: Pre-trigger mode
Post-trigger mode (snap shot))

Fig. 41: Post-trigger mode