X64-AN Quad User's Manual
Theory of Operation
53
On
X64-AN Quad
, the external trigger is protected by an opto-coupler. A minimum pulse width of 10
μ
s
is necessary to detect an active high trigger pulse while a minimum pulse width of 50
μ
s is required for
an active low trigger pulse. The
X64-AN Quad
is also equipped with signal debounce input circuit that
allows the user to define the minimum acceptable pulse width via Sapera
(CORACQ_PRM_EXTERNAL_TRIGGER_DURATION).
The region where an External Trigger will be ignored can be programmed using the 2 parameters
CORACQ_PRM_EXT_TRIGGER_IGNORE_DELAY and
CORACQ_PRM_CAM_CONTROL_DURING_READOUT.
Vertical Sync from Camera
The Vertical Sync event indicates a vertical sync has been detected. Note that this does not necessarily
mean the image will be captured. For instance, if you have a free-running camera at 30 fps with
external trigger enabled, you will get 30 events per second even though the
X64-AN Quad
waits for an
external trigger to actually capture the next image. This allows the application program to
independently count frames coming from the camera. The Sapera event value is
CORACQ_VAL_EVENT_TYPE_VERTICAL_SYNC.
Horizontal Sync (Lock/Unlock)
The Horizontal Sync Lock/Unlock event indicates the state of the Analog to Digital Converter PLL
with respect to the incoming horizontal sync. In order to digitize accurately, the PLL must be
synchronized (i.e. be locked) to the incoming video HS. This interrupt is available when video is
connected to the
X64-AN Quad
, whether it is acquiring images or not. In addition, a corresponding
status flag can be read from the acquisition module. Typically the application first verifies the HS lock
condition before starting an acquisition sequence.
The Sapera event values are CORACQ_VAL_EVENT_TYPE_HSYNC_LOCK and
CORACQ_VAL_EVENT_TYPE_HSYNC_UNLOCK.
The Sapera status values are CORACQ_VAL_SIGNAL_HSYNC_LOCK and
CORACQ_VAL_SIGNAL_HSYNC_UNLOCK.
Data Overflow
The Data Overflow event indicates that there is not enough bandwidth for the acquired data to flow.
This is usually caused by limitations of the acquisition module. Since the
X64-AN Quad
can easily
sustain onboard data transfers over 320MB, data overflow should never occur. The Sapera event value
is CORACQ_VAL_EVENT_TYPE_DATA_OVERFLOW.
Frame Lost
The Frame Lost event indicates that an acquired image could not be transferred to onboard memory.
An example of this case would be if there are no free onboard buffers available for the new image.
This will usually be the case if the image transfer from onboard buffers to host PC memory cannot be
sustained due to the PCI bus bandwidth. If multiple PCI bus master devices are active simultaneously,
it is possible that the
X64-AN Quad
PCI controller can not transfer onboard buffers in time for the next
