6. Trigger 73
Note
The delay set through TriggerDelay forces LinePeriod to increment.
Please check if resulting LinePeriod is still suitable for the application.
6.6.1 Encoder delay
Acquisition-start trigger and frame-start trigger can also delay the signaling of the trigger event for an
amount of encoder steps, set through the module’s EncoderDelay property.
The granularity of EncoderDelay is 1 encoder step.
When using EncoderDelay, TriggerDelay should be set to 0. If not, trigger event will be delayed by
an additional TriggerDelay time after encoder required displacement.
6.6.2 Trigger overrun
Each trigger module generates its own ready signal indicating that it is able to receive a new trigger:
• AcquisitionStartTriggerReady
• FrameStartTriggerReady
• LineStartTriggerReady
• ExposureEndTriggerReady
These signals are named after the generating trigger module and can be sent to the output ports. You
can also identify when the exposure is in progress by checking the exposure signal status.
A trigger module accepts an input signal only when its trigger-ready signal is active; trigger signals are
otherwise ignored and increment an overrun counter. You can learn how many triggers have not been
accepted by a trigger module through the TriggerErrors (read-only) property related to that trigger
module.
Example Code 6.2 | Usage of the TriggerErrors property
if (device.FrameStartTrigger.TriggerErrors > 0)
Debug.WriteLine("Invalid triggers detected.");
Figure 6.2 shows a possible timing of exposure and line-start-trigger-related signals.
The exposure begins after the specied trigger delay and a new trigger signal can be accepted only when
LineStartTriggerReadyis asserted. After receiving a valid trigger, the trigger-ready signal goes low,
indicating that the requested exposure is being processed.
The second trigger in the picture is ignored as the LineStartTriggerReady signal is still low; the
error condition is detected and increments the trigger overrun counter.
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