VDP3108 datasheet(20/61 Pages) MICRONAS

20 / 61 page

VDP 3108

ADVANCE INFORMATION

MICRONAS INTERMETALL

2.6.1. Video Sync Processing

Fig. 2–25 shows a block diagram of the front end sync

processing. To extract the sync information from the

video signal, a linear phase lowpass filter eliminates all

noise and video contents above one MHz. The sync is

separated by a slicer, the sync phase is measured. A

variable window can be selected to improve the noise

immunity of the slicer. The phase comparator measures

the falling edge of sync as well as the integrated sync

pulse.

The sync phase error is filtered by a phase locked loop

that is computed by the FP. All timing in the front end is

derived from a counter that is part of this PLL and it thus

counts synchronously to the video signal.

A separate hardware block measures the signal back

porch and also allows to gather maximum/minimum of

the video signal. This information is processed by the FP

and used for of gain control and clamping.

For vertical sync separation the sliced video signal is in-

tegrated. The FP uses the integrator value to derive ver-

tical sync and field information.

The information extracted by the video sync processing

is multiplexed onto the hardware front sync signal (FSY)

and is distributed to the rest of the video processing sys-

tem. The format of the front sync signal is given in fig.

2–26.

The data for the vertical deflection, the sawtooth and the

East-West correction signal is calculated by the FP. The

data is buffered in a FIFO and transferred to the back

end by a single wire interface.

phase

comparator

lowpass

counter

frontend

timing

FSY

lowpass

1 MHz

syncslicer

horizontal

sync

separation

vertical

sync

separation

FIFO

Sawtooth

video

input

skew

front

sync

generator

vertical

serial

data

VDATA

sawtooth

E/W

Parabola

Calculation

clamping, colorkey, FIFO_write

PLL1

clamp &

signal

meas.

Fig. 2–25: Sync separation block diagram

v blank

even field

(not in scale)

input

analog

video

FSY

Parity

Vert. blanking

0 = off

1 = on

Field #

0 = field 1

1 = field 2

Fig. 2–26: Front sync format

skew

MSB

skew

LSB

not

used

F0, F2..F5 reserved

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