AD9984AKSTZ-170 View Datasheet(PDF) - Analog Devices

Part Name

Description

Manufacturer

AD9984AKSTZ-170

500 MSPS Direct Digital Synthesizer

Analog Devices 

AD9984A

HSYNCIN

FILTER

WINDOW

HSYNCOUT

VSYNC

EQUALIZATION

PULSES

EXPECTED

EDGE

FILTER

WINDOW

Figure 11. Sync Processing Filter

Vsync Filter and Odd/Even Fields

The Vsync filter is used to eliminate spurious Vsyncs, maintain

a stable timing relationship between the Vsync and Hsync

output signals, and generate the odd/even field output.

The filter works by examining the placement of Vsync with

respect to Hsync and if necessary, shifting it in time slightly.

The goal is to keep the Vsync and Hsync leading edges from

switching at the same time, thus eliminating confusion as to

when the first line of a frame occurs. Register 0x14, Bit 2 enables

the Vsync filter. Use of the Vsync filter is recommended for all

cases, including interlaced video, and is required when using

the Hsyncs per Vsync counter. Figure 12 and Figure 13 illustrate

even/odd field determination in two situations.

SYNC SEPERATOR THRESHOLD

QUADRANT

HSYNCIN

VSYNCIN

FIELD 1

2

3

FIELD 0

4

1

FIELD 1

2

3

VSYNCOUT

O/E FIELD

EVEN FIELD

Figure 12. Even Field

SYNC SEPERATOR THRESHOLD

FIELD 0

4

1

QUADRANT

HSYNCIN

VSYNCIN

FIELD 1

2

3

VSYNCOUT

O/E FIELD

Rev. 0 | Page 18 of 44

FIELD 0

4

1

FIELD 1

2

3

ODD FIELD

Figure 13. Odd Field

FIELD 0

4

1

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