vpx3224d ETC-unknow, vpx3224d Datasheet - Page 26

• Manufacturer Part Number: vpx3224d
• Description: Video Pixel Decoders
• Manufacturer: ETC-unknow

26
VPX 3225D, VPX 3224D
2.9. Operational Modes
The relationship between the video timing signals
(HREF and VREF) and the analog input video is deter-
mined by the selected operational mode. Three such
modes are available: the Open Mode, the Forced
Mode, and the Scan Mode. These modes are selected
via I
2.9.1. Open Mode
In the Open Mode, both the HREF and the VREF signal
track the analog video input. In the case of a change in
the line standard (i.e. switching between the video input
ports), HREF and VREF automatically synchronize to
the new input. When no video is present, both HREF and
VREF float to the idling frequency of their respective
PLLs. During changes in the video input (drop-out,
switching between inputs), the performance of the
HREF and VREF signals is not guaranteed.
VREF
Fig. 2–30: Transition between timing standards
2
C commands [FP-RAM 0x140, settm, lattm].
I
switch video timing standard
2
C Command to
f
16.683 ms
odd
33.367 ms
(525/60)
f
even
Selected timing standard
becomes active
f
odd
20.0 ms
2.9.2. Scan Mode
In the Scan Mode, the HREF and VREF signals are al-
ways generated by free running hardware. They are
therefore completely decoupled from the analog input.
The output video data is always suppressed.
The purpose of the Scan Mode is to allow the external
controller to freely switch between the analog inputs
while searching for the presence of a video signal. In-
formation regarding the video (standard, source, etc...)
can be queried via I
In the Scan Mode, the video line standard of the VREF
and HREF signals can be changed via I
The transition always occurs at the first frame boundary
after the I
demonstrates the behavior of the VREF signal during
the transition from the 525/60 system to the 625/50 sys-
tem (the width of the vertical reference pulse is exagger-
ated for illustration).
(625/50)
40.0 ms
2
C command is received. Fig. 2–30, below,
f
even
2
C read.
PRELIMINARY DATA SHEET
time
f
odd
2
C command.
Micronas