Data Sheet
ADV7180
When AUTO_PDC_EN is 1 (default), the ADV7180 automatically
determines the LTA and CTA values to have luma and chroma
aligned at the output.
BL_C_VBI, Blank Chroma During VBI, Address 0x04[2]
Setting BL_C_VBI high blanks the Cr and Cb values of all VBI
lines. This is done so any data that may arrive during VBI is not
decoded as color and is output through Cr and Cb. As a result,
it is possible to send VBI lines into the decoder and then output
them through an encoder again, undistorted. Without this
blanking, any color that is incorrectly decoded would be encoded
by the video encoder, thus distorting the VBI lines.
LTA[1:0], Luma Timing Adjust, Address 0x27[1:0]
The luma timing adjust register allows the user to specify a
timing difference between chroma and luma samples.
There is a functionality overlap with the CTA[2:0] register. For
manual programming, use the following defaults:
Setting BL_C_VBI to 0 decodes and outputs color during VBI.
•
•
•
CVBS input LTA[1:0] = 00
Y/C input LTA[1:0] = 01
YPrPb input LTA[1:0] = 01
Setting BL_C_VBI to 1 (default) blanks Cr and Cb values
during VBI.
Range, Range Selection, Address 0x04[0]
Table 62. LTA Function
AV codes (as per ITU-R BT.656, formerly known as CCIR-656)
consist of a fixed header made up of 0xFF and 0x00 values.
These two values are reserved and, therefore, are not to be used
for active video. Additionally, the ITU specifies that the nominal
range for video should be restricted to values between 16 and
235 for luma and 16 and 240 for chroma.
LTA[1:0]
Description
00 (default)
No delay
01
10
11
Luma 1 clock (37 ns) late
Luma 2 clock (74 ns) early
Luma 1 clock (37 ns) early
CTA[2:0], Chroma Timing Adjust, Address 0x27[5:3]
The range bit allows the user to limit the range of values output
by the ADV7180 to the recommended value range. The
ADV7180 does not scale the data to fit within the smaller range.
Any value outside of the range is ignored. In any case, it ensures
that the reserved values of 255d (0xFF) and 00d (0x00) are not
presented on the output pins unless they are part of an AV code
header.
The chroma timing adjust register allows the user to specify a
timing difference between chroma and luma samples. This can
be used to compensate for external filter group delay differences
in the luma vs. chroma path and to allow a different number of
pipeline delays while processing the video downstream. Review
this functionality together with the LTA[1:0] register.
The chroma can be delayed or advanced only in chroma pixel
steps. One chroma pixel step is equal to two luma pixels. The
programmable delay occurs after demodulation, where delay
cannot be made by luma pixel steps.
Table 61. RANGE Function
Range
Description
0
16 ≤ Y ≤ 235, 16 ≤ C/P ≤ 240
1 ≤ Y ≤ 254, 1 ≤ C/P ≤ 254
1 (default)
For manual programming, use the following defaults:
AUTO_PDC_EN, Automatic Programmed Delay Control,
Address 0x27[6]
•
•
•
CVBS input CTA[2:0] = 011
Y/C input CTA[2:0] = 101
YPrPb input CTA[2:0] = 110
Enabling AUTO_PDC_EN activates a function within the
ADV7180 that automatically programs the LTA[1:0] and CTA[2:0]
registers to have the chroma and luma data match delays for all
modes of operation. If AUTO_PDC__EN is set, the LTA[1:0]
and CTA[2:0] manual registers are not used. If the automatic
mode is disabled (by setting the AUTO_PDC_EN bit to 0), the
values programmed into the LTA[1:0] and CTA[2:0] registers
become active.
Table 63. CTA Function
CTA[2:0]
Description
000
Not a valid setting
001
010
011 (default)
100
101
Chroma + two pixels (early)
Chroma + one pixel (early)
No delay
Chroma − one pixel (late)
Chroma − two pixels (late)
Chroma − three pixels (late)
Not a valid setting
When AUTO_PDC_EN is 0, the ADV7180 uses the LTA[1:0] and
CTA[2:0] values for delaying luma and chroma samples. See the
LTA[1:0], Luma Timing Adjust, Address 0x27[1:0] section and
the CTA[2:0], Chroma Timing Adjust, Address 0x27[5:3]
section.
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Rev. G | Page 45 of 120
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