402-00005-00
Theory of Operation
2–6
Rev 02; February 8, 2002
FEN
Field
ACQMD = 0
ACQMD = 2
Acquire
bits
valid data acquired
Data
Grab status
status shows snap
in progress
snap requested
odd
even
odd
even
odd
Figure 2–3. Interlaced Acquire
2.3.1.2 External Trigger Acquisition
External Trigger allows image acquisition to be synchronized to external events. When acquiring an image in exter-
nal trigger mode, the acquisition will not start until the PCVisionplus receives a trigger signal. Acquisition begins
with the next valid frame after the trigger. When performing external trigger acquisition, be sure the starting field bits
are set for next field. Figure 2–4 shows an example of triggered acquire. The trigger input remains armed after the
acquire completes, ready for the next trigger input.
FEN
Field
ACQMD = 0
ACQMD = 2
Acquire
bits
Data
Grab status
snap requested
odd
even
odd
even
odd
external
trigger
valid data
Figure 2–4. Triggered Acquire
2.3.1.3 Multiple Frame Acquire Mode
PCVisionplus has the ability to acquire and store up to eight images sequentially into image memory, with the execu-
tion of one snap command. Program the Frame Count bits (FCNT) to the desired number of frames (1 to 8). For
non-interlaced or interlaced acquisitions the multiple acquire mode count (FCNT) always refers to full frames.
In Normal mode, the frame count is set for 1 to 8 images. When a Snap command is executed, the programmed
number of images is acquired sequentially into a memory frame. In Grab mode, the program number of images is
acquired and then the acquire address resets back to the Start of Acquire address, and continues, overwriting the
previous images. It is also possible to disable this reset to the Start of Acquire address, and the acquire continues
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