adv7718 Analog Devices, Inc., adv7718 Datasheet - Page 12

• Manufacturer Part Number: adv7718
• Description: Integrated Digital Ccir-601 Pal/ntsc Video Encoder
• Manufacturer: Analog Devices, Inc.

ADV7177/ADV7178
DATA PATH DESCRIPTION
For PAL B, D, G, H, I, M, N and NTSC M, N modes, YCrCb
4:2:2 data is input via the CCIR-656 compatible pixel port at a
27 MHz data rate. The pixel data is demultiplexed to from three
data paths. Y typically has a range of 16 to 235, Cr and Cb typi-
cally have a range of 128 ± 112; however, it is possible to input data
from 1 to 254 on both Y, Cb and Cr. The ADV7177/ADV7178
supports PAL (B, D, G, H, I, N, M) and NTSC (with and without
Pedestal) standards. The appropriate SYNC, BLANK and Burst
levels are added to the YCrCb data. Macrovision antitaping
(ADV7178 only), closed captioning, OSD (ADV7177 only),
and teletext levels are also added to Y, and the resultant data is
interpolated to a rate of 27 MHz. The interpolated data is filtered
and scaled by three digital FIR filters.
The U and V signals are modulated by the appropriate subcarrier
sine/cosine phases and added together to make up the chrominance
signal. The luma (Y) signal can be delayed 1–3 luma cycles (each
cycle is 74 ns) with respect to the chroma signal. The luma and
chroma signals are then added together to make up the composite
video signal. All edges are slew rate limited.
The YCrCb data is also used to generate RGB data with
appropriate SYNC and BLANK levels. The RGB data is in
synchronization with the composite video output. Alternatively
analog YUV data can be generated instead of RGB.
–10
–20
–30
–40
–50
–60
0
0
2
4
FREQUENCY – MHz
6
8
10
12
The three 9-bit DACs can be used to output:
1. RGB Video
2. YUV Video
3. One Composite Video Signal + LUMA and CHROMA
3.
Alternatively, each DAC can be individually powered off if
not required.
Video output levels are illustrated in Appendix 3.
INTERNAL FILTER RESPONSE
The Y filter supports several different frequency responses,
including two 4.5 MHz/5.0 MHz low-pass responses, PAL/
NTSC subcarrier notch responses and a PAL/NTSC extended
response. The U and V filters have a 1.0/1.3 MHz low-pass
response for NTSC/PAL. These filter characteristics are illus-
trated in the Typical Performance Characteristics (TPCs 1 to 7).
COLOR BAR GENERATION
The ADV7177/ADV7178 can be configured to generate 100/7.5/
75/7.5 color bars for NTSC or 100/0/75/0 for PAL color bars. These
are enabled by setting MR17 of Mode Register 1 to Logic “1.”
Square Pixel Mode
The ADV7177/ADV7178 can be used to operate in square pixel
mode. For NTSC operation an input clock of 24.5454 MHz is
required. Alternatively an input clock of 29.5 MHz is required
for PAL operation. The internal timing logic adjusts accordingly
for square pixel mode operation.
Color Signal Control
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.
(S-Video).