adv7194 Analog Devices, Inc., adv7194 Datasheet - Page 19
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adv7194
Manufacturer Part Number
adv7194
Description
Professional Extended-10? Video Encoder With 54 Mhz Oversampling
Manufacturer
Analog Devices, Inc.
Datasheet
1.ADV7194.pdf
(69 pages)
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The progressive scan decoder deinterlaces the data from the
MPEG2 decoder. This now means that there are 525 video lines
per field in NTSC mode and 625 video lines per field in PAL
mode. The duration of the video line is now 32 µs.
It is important to note that the data from the MPEG2 decoder is
in 4:2:2 format. The data output from the progressive scan decoder
is in 4:4:4 format. Thus it is assumed that some form of interpola-
tion on the color component data is performed in the progressive
scan decoder IC. (Mode Register 8.)
REAL-TIME CONTROL, SUBCARRIER RESET AND
TIMING RESET
Together with the SCRESET/RTC/TR pin and of Mode
Register 4 (Genlock Control), the ADV7194 can be used in
(a) Timing Reset Mode, (b) Subcarrier Phase Reset Mode or
(c) RTC Mode.
(a) A TIMING RESET is achieved in holding this pin high. In
(b) The SUBCARRIER PHASE will reset to that of Field 0 at
(c) In RTC MODE, the ADV7194 can be used to lock to an
The real-time control mode allows the ADV7194 to auto-
matically alter the subcarrier frequency to compensate for
line length variations. When the part is connected to a device
that outputs a digital datastream in the RTC format (such
as an ADV7185 video decoder, see Figure 37), the part will
automatically change to the compensated subcarrier fre-
quency on a line-by-line basis. This digital datastream is
67 bits wide and the subcarrier is contained in Bits 0 to 21.
Each bit is two clock cycles long. 00Hex should be written
into all four Subcarrier Frequency registers when using this
mode. It is recommended to use the ADV7185 in this mode
(Mode Register 4.)
this state the horizontal and vertical counters will remain
reset. On releasing this pin (set to low), the internal counters
will commence counting again. The minimum time the pin
has to be held high is 37 ns (1 clock cycle at 27 MHz),
otherwise the reset signal might not be recognized.
the start of the following field when a low to high transition
occurs on this input pin.
external video source.
MPEG2
PROGRESSIVE
DECODER
27MHz
SCAN
PIXEL BUS
30-BIT INTERFACE
ADV7194
PLL
ENCODER
CORE
54MHz
2
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SCH PHASE MODE
The SCH phase is configured in default mode to reset every
four (NTSC) or eight (PAL) fields to avoid an accumulation of
SCH phase error over time. In an ideal system, zero SCH phase
error would be maintained forever, but, in reality, this is impossible
to achieve due to clock frequency variations. This effect is reduced
by the use of a 32-bit DDS, which generates this SCH.
Resetting the SCH phase every four or eight fields avoids the
accumulation of SCH phase error, and results in very minor
SCH phase jumps at the start of the four or eight field sequence.
Resetting the SCH phase should not be done if the video source
does not have stable timing or the ADV7194 is configured in RTC
mode. Under these conditions (unstable video) the Subcarrier
Phase Reset should be enabled but no reset applied. In this
configuration the SCH Phase will never be reset; this means
that the output video will now track the unstable input video. The
Subcarrier Phase Reset when applied will reset the SCH phase
to Field 0 at the start of the next field (e.g., Subcarrier Phase
Reset applied in Field 5 (PAL) on the start of the next field SCH
phase will be reset to Field 0). (Mode Register 4.)
SLEEP MODE
If, after RESET, the SCRESET/RTC/TR and NTSC_PAL pins
are both set high, the ADV7194 will power-up in Sleep Mode to
facilitate low-power consumption before all registers have been
initialized.
If Power-up in Sleep Mode is disabled, Sleep Mode control
passes to the Sleep Mode control in Mode Register 2 (i.e., con-
trol via I
SQUARE PIXEL MODE
The ADV7194 can be used to operate in square pixel mode. For
NTSC operation an input clock of 24.5454 MHz is required.
Alternatively, for PAL operation, an input clock of 29.5 MHz
is required. The internal timing logic adjusts accordingly for
square pixel mode operation. Square pixel mode is not available
in 4× Oversampling mode. (Mode Register 2.)
VERTICAL BLANKING DATA INSERTION AND BLANK
INPUT
It is possible to allow encoding of incoming YCbCr data on
those lines of VBI that do not have line sync or pre-/post-equal-
ization pulses. This mode of operation is called Partial Blanking. It
allows the insertion of any VBI data (Opened VBI) into the
encoded output waveform, this data is present in digitized
incoming YCbCr data stream (e.g., WSS data, CGMS, VPS
etc.). Alternatively the entire VBI may be blanked (no VBI data
inserted) on these lines. VBI is available in all timing modes.
It is possible to allow control over the BLANK signal using
Timing Register 0. When the BLANK input is enabled (TR03 =
0 and input pin tied low), the BLANK input can be used to
input externally generated blank signals in Slave Mode 1, 2, or
3. When the BLANK input is disabled (TR03 = 1 and input pin
tied low or tied high) the BLANK input is not used and the
ADV7194 automatically blanks all normally blank lines as per
CCIR-624. (Timing Register 0.)
2
C). (Mode Register 2 and Mode Register 6.)
ADV7194