Data Translation DT3152-LS, User Manual

Page: 42 / 214

Chapter 2
26
Sync Sentinel
Note: The Sync Sentinel can be used for area-scan operations only.
It cannot be used for line-scan operations.
The Sync Sentinel circuitry allows you to control when sync signals
occur on the DT3152-LS frame grabber board. This is especially
useful for noisy input sources, such as VCRs, where the DT3152-LS
board may interpret a noise spike in the video signal as a horizontal
or vertical sync, or the board may miss some syncs that are below the
threshold.
You can enable or disable the Sync Sentinel through software. By
default, the Sync Sentinel is enabled.
When the Sync Sentinel is enabled, you determine the window in
which a sync can be detected by specifying a horizontal search
position, a horizontal insert position, a vertical search position, and a
vertical insert position.
The horizontal sync search position is the pixel location within a line
at which the DT3152-LS board begins to search for the horizontal
sync. If the horizontal sync is not detected before the horizontal sync
insert position is reached, the board inserts a horizontal sync to
synchronize to the video signal. The default value for the horizontal
search position is 95.0% of the total pixels per line. The default value
for the horizontal insert position is 101.5% of the total pixels per line.
The vertical sync search position is the line location within a field at
which the DT3152-LS board begins to search for the vertical sync. If
the vertical sync is not detected before the vertical sync insert
position is reached, the board inserts a vertical sync to stay in sync
with the video signal. The default value for the vertical search