Analog Devices Advantiv ADV7604 Hardware Manual page 316

The ADV7604 has two main modes of operation: external clamp mode 1 and external clamp mode:
• In external clamp mode 1:
DFC is enabled for the user to clamp the pedestal level to the lowest digital code by digitally
subtracting the digitized synchronization portion.
• In external clamp mode 2:
DFC is disabled to give the user the option to output the full digitized video signal available
(including the digitized synchronization signal).
Note: If the user prefers to have DFC enabled and also have full video signal output (including the
digitized synchronization signal), the user needs to program the gain and the offset value manually to
fit in the full video signal to the digital output range.
For oversampled modes such as 2x1 and 4x1 modes, there are two options for providing the
sampling clock.
In standard external clock and clamp modes, the 2x or 4x clock must be provided externally via the
EXT_CLK pin.
In US-external clamp modes, the external clock provided via the EXT_CLK pin is a 1x sampling
clock. This 1x clock is then used to generate internally a 2x or 4x sampling clock as required by the
programmed mode.
Refer to Table 64 for programming of the required external clock and clamp mode.
Notes:
• In 1x1 external clock and clamp modes, the CP_CSC is enabled and can be used for color
space conversion
• The CP_CSC is not available in other external clock and clamp modes
EXT_VCLMP_REGEN, CP Map, Address 0xC5, [4]
The EXT_VCLMP_REGEN bit controls the selection of external clamp mode in between
regeneration and nonregeneration mode, as described in Section 10.16.
Function
EXT_VCLMP_RE
GEN
0
1
Rev. F August 2010
Description
Nonregeneration mode (direct clamp control with external clamp pulse)
Regeneration mode (clamp control with regenerated clamp pulse)
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ADV7604