EVAL-AD9880-ABZ Analog Devices Inc, EVAL-AD9880-ABZ Datasheet - Page 43

• Manufacturer Part Number: EVAL-AD9880-ABZ
• Description: Video Input Module Kit AD9880
• Manufacturer: Analog Devices Inc

Specifications of EVAL-AD9880-ABZ

• Main Purpose: Video, Video Processing
• Embedded: No
• Utilized Ic / Part: AD9880
• Primary Attributes: HDMI Receiver & Analog Interface
• Secondary Attributes: Triple 8-bit 150MSPS ADC's
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

0x20
0x21
Table 35. Sync Processing Filter Enable
Select
0
1
0x21
Table 36. PLL Sync Filter Enable
Select
0
1
0x21
7-0
This 8-bit register sets the distance in 40 MHz clock
periods (25 ns), which is the allowed distance for
Hsync pulses before and after the expected Hsync
edge. This is the heart of the filter in that it only looks
for Hsync pulses at a given time (plus or minus this
window) and then ignores extraneous equalization
pulses that disrupt accurate PLL operation. The
power-up default setting is 10d, or 200 ns on either
side of the expected Hsync.
7
This bit selects which Hsync is used for the sync
processing functions of internal Coast, H/V count,
field detection, and Vsync duration counts. A clean
Hsync is fundamental to accurate processing of the
sync. The power-up default setting is 1.
6
This bit selects which signal the PLL uses. It can select
between raw Hsync or SOG, or filtered versions. The
filtering of the Hsync and SOG can eliminate nearly
all extraneous transitions which have traditionally
caused PLL disruption. The power-up default setting
is 0.
5
The purpose of the Vsync filter is to guarantee the
position of the Vsync edge with respect to the Hsync
edge and to generate a field signal. The filter works by
examining the placement of Vsync and regenerating a
correctly placed Vsync one line later. The Vsync is
first checked to see whether it occurs in the Field 0
position or the Field 1 position. This is done by
checking the leading edge position against the sync
separator threshold and the Hsync position. The
Hsync width is divided into four quadrants with
Quadrant 1 starting at the Hsync leading edge plus a
sync separator threshold. If the Vsync leading edge
occurs in Quadrant 1 or 4 then the field is set to 0 and
the output Vsync is placed coincident with the Hsync
leading edge. If the Vsync leading edge occurs in
Quadrant 2 or 3 then the field is set to 1 and the
output Vsync leading edge is placed in the center of
the line. In this way, the Vsync filter creates a
Result
Sync processing uses raw Hsync or SOG
Sync processing uses regenerated Hsync from sync
filter
Result
PLL uses raw Hsync or SOG inputs
PLL uses filtered Hsync or SOG inputs
Sync Filter Window Width
Sync Processing Filter Enable
PLL Sync Filter Enable
Vsync Filter Enable
Rev. 0 | Page 43 of 64
Table 37. Vsync Filter Enable
Vsync Filter Bit
0
1
0x21
Table 38. Vsync Duration Enable
Vsync
Duration Bit
0
1
0x21
Table 39. AO Clamp Mode
AO
Offset Mode
0
1
0x21
Table 40. AO Clamp Length
AO Offset
Clamp Bit
0
1
0x22
predictable relative position between Hsync and
Vsync edges at the output.
If the Vsync occurs near the Hsync edge, this guaran-
tees that the Vsync edge follows the Hsync edge. This
performs filtering also in that it requires a minimum
of 64 lines between Vsyncs. The Vsync filter cleans up
extraneous pulses that might occur on the Vsync. This
should be enabled whenever the Hsync/Vsync count is
used. Setting this bit to 0 disables the Vsync filter.
Setting this bit to 1 enables the Vsync filter. Power-up
default is 0.
4
This enables the Vsync duration block which is
designed to be used with the Vsync filter. Setting the
bit to 0 leaves the Vsync output duration unchanged;
setting the bit to 1 sets the Vsync output duration
based on Register 0x22. The power-up default is 0.
3
This bit specifies if the auto offset measurement takes
place during clamp or either 10 or 16 clocks afterward.
The measurement takes 6 clock cycles.
2
This bit sets the delay following the end of the clamp
period for AO measurement. This bit is valid only if
Register 0x21, Bit 3 = 1.
7-0
This is used to set the output duration of the Vsync,
and is designed to be used with the Vsync filter. This
is valid only if Register 0x21, Bit 4 is set to 1. Power-up
default is 4.
Result
Delay is 10 clock cycles
Delay is 16 clock cycles
Result
Auto offset measurement takes place during
clamp period
Auto offset measurement is set by 0x21, Bit 2
Vsync Duration Enable
Auto Offset Clamp Mode
Auto Offset Clamp Length
Vsync Duration
Result
Vsync filter disabled
Vsync filter enabled
Result
Vsync output duration unchanged
Vsync output duration set by 0x22
AD9880