cx25840 Conexant Systems, Inc., cx25840 Datasheet - Page 69

• Manufacturer Part Number: cx25840
• Description: Video Decoder And Broadcast Audio
• Manufacturer: Conexant Systems, Inc.

CX25840/1/2/3 Data Sheet
3.6.3
Figure 3-14. Typical VBI Waveform
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Slice Level
VBI Waveform Description
HDELAY
COLOR
BURST
A detailed description of the incoming waveform will help to better understand the
VBI function blocks. The model that is being used for the VBI block implementation
is based on four basic input data formats: Closed Caption (CC), Wide Screen
Signaling (WSS), Teletext (TTX), and VITC. All other signaling standards should fit
into the format of these signals.
Figure 3-14
illustrate the various signaling formats and how the various sections of the signal play
a part into the VBI engine. The VBI engine starts when one of the following three
events occurs: a vertical reset, time-out of data run-in, or the end of the previous line’s
data capture mode.
There are exceptions to the typical VBI waveform shown in
VBI standards such as WSS525, VITC525, and VITC625 do not have clock run-in
periods. Another VBI standard that differs from the example given is the WSS625
VBI standard. It is a biphase modulated signal.
depicts a Closed Caption waveform. The main purpose of this figure is to
Clock Run-in
Conexant
Start/Frame
Code
S
A
R
T
T
D0-D6
Data Capture
P
A
R
Y
T
Figure
I
Detailed Functional Description
D0-D6
3-14. For example,
R
P
A
T
Y
I
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