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Theory of Operation
X64-AN Quad User's Manual
Trigger Signal Validity
External trigger signal noise or glitches are easily ignored by the ACU with its programmable
debounce control. A parameter is programmed for the minimum pulse duration considered as a valid
external trigger pulse. Refer to
“
” on page 41
for more information.
Acquisition Events
Acquisition events are related to the acquisition module. They provide feedback on the image
digitization phase. The following block diagram illustrates the acquisition process.
A/D
Onboard
Memory
Trigger
Camera
Start of
image
End of image
capture
End of PCI
transfer
PCI
Controller
Host
Memory
Figure 30: Acquisition/Transfer Interrupts
Event-Related Definitions
Interrupt
An interrupt is a signal sent by the X64-AN Quad board to the computer CPU
which indicates an event on the frame grabber. The X64-AN Quad driver has
excellent event reaction time since interrupts are processed inside an interrupt
service routine (ISR) at kernel level.
Event
An event is a WIN32 object that can take two states: signaled and non-signaled. It
is used for thread synchronization. In this context, an event is associated with an
interrupt so that a WIN32 thread can be unblocked when the event it is waiting for
gets signaled. For example, when an interrupt is received, the corresponding event
is signaled and the thread waiting for this event resumes execution.
External Trigger (Used/Ignored)
The External Trigger event is generated when the external trigger pin is asserted, usually indicating the
start of the acquisition process. There are 2 types of external trigger events: ‘Used’ or ‘Ignored’.
Following an external trigger, if the event generates a captured image, an External Trigger Used event
will be generated (CORACQ_VAL_EVENT_TYPE_EXTERNAL_TRIGGER).
If there is no captured image, an External Trigger Ignored event will be generated
(CORACQ_VAL_EVENT_TYPE_EXTERNAL_TRIGGER_IGNORED). An external trigger event
will be ignored if the rate at which the events are received are higher than the possible frame rate of
the camera.
