ADV7170/ADV7171
0
–10
SUBCARRIER RESET
–20
MAGNITUDE – dB
–30
–40
Together with the SCRESET/RTC pin, and bits MR22 and
MR21 of Mode Register 2, the ADV7170/ADV7171 can be
used in subcarrier reset mode. The subcarrier will reset to Field
0 at the start of the following field when a low-to-high transition
occurs on this input pin.
REAL-TIME CONTROL
–50
–60
–70
0
2
4
6
8
FREQUENCY – MHz
10
12
Figure 18. QCIF Chroma Filter
COLOR BAR GENERATION
The ADV7170/ADV7171 can be configured to generate 75%
amplitude, 75% saturation (75/7.5/75/7.5) for NTSC or 75%
amplitude, 100% saturation (100/0/75/0) for PAL color bars.
These are enabled by setting MR17 of Mode Register 1 to
Logic “1.”
SQUARE PIXEL MODE
Together with the SCRESET/RTC pin, and Bits MR22 and
MR21 of Mode Register 2, the ADV7170/ADV7171 can be
used to lock to an external video source. The real-time control
mode allows the ADV7170/ADV7171 to automatically alter the
subcarrier frequency to compensate for line length variation.
When the part is connected to a device that outputs a digital
datastream in the RTC format (such as a ADV7185 video de-
coder, see Figure 19), the part will automatically change to the
compensated subcarrier frequency 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 2 clock cycles long. 00Hex should be
written into all four subcarrier frequency registers when using
this mode.
VIDEO TIMING DESCRIPTION
The ADV7170/ADV7171 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 accord-
ingly for square pixel mode operation.
COLOR SIGNAL CONTROL
The ADV7170/ADV7171 is intended to interface to off-
the-shelf MPEG1 and MPEG2 Decoders. Consequently, the
ADV7170/ADV7171 accepts 4:2:2 YCrCb Pixel Data via a
CCIR-656 pixel port and has several video timing modes of
operation that allow it to be configured as either system master
video timing generator or a slave to the system video timing
generator. The ADV7170/ADV7171 generates all of the re-
quired horizontal and vertical timing periods and levels for the
analog video outputs.
The ADV7170/ADV7171 calculates the width and placement of
analog sync pulses, blanking levels and color burst envelopes.
Color bursts are disabled on appropriate lines, and serration and
equalization pulses are inserted where required.
In addition, the ADV7170/ADV7171 supports a PAL or NTSC
square pixel operation in slave mode. The part requires an input
pixel clock of 24.5454 MHz for NTSC and an input pixel clock
of 29.5 MHz for PAL. The internal horizontal line counters
place the various video waveform sections in the correct location
for the new clock frequencies.
The ADV7170/ADV7171 has four distinct master and four
distinct slave timing configurations. Timing Control is estab-
lished with the bidirectional
SYNC, BLANK
and FIELD/
VSYNC
pins. Timing Mode Register 1 can also be used to vary
the timing pulsewidths and where they occur in relation to each
other.
The color information can be switched on and off the video
output using Bit MR24 of Mode Register 2.
BURST SIGNAL CONTROL
The burst information can be switched on and off the video
output using Bit MR25 of Mode Register 2.
NTSC PEDESTAL CONTROL
The pedestal on both odd and even fields can be controlled on a
line-by-line basis using the NTSC Pedestal Control Registers.
This allows the pedestals to be controlled during the vertical
blanking interval (Lines 10 to 25 and Lines 273 to 288).
PIXEL TIMING DESCRIPTION
The ADV7170/ADV7171 can operate in either 8-bit or
16-bit YCrCb Mode.
8-Bit YCrCb Mode
This default mode accepts multiplexed YCrCb inputs through
the P7-P0 pixel inputs. The inputs follow the sequence Cb0, Y0
Cr0, Y1 Cb1, Y2, etc. The Y, Cb and Cr data are input on a
rising clock edge.
16-Bit YCrCb Mode
This mode accepts Y inputs through the P7–P0 pixel inputs and
multiplexed CrCb inputs through the P15–P8 pixel inputs. The
data is loaded on every second rising edge of CLOCK. The inputs
follow the sequence Cb0, Y0 Cr0, Y1 Cb1, Y2, etc.
REV. 0
–13–
AD [ ANALOG DEVICES ]
