GS1881 Datasheet, PDF (14/14 Pages) Gennum Corporation – Monolithic Video Sync Separators

(3) Deriving Odd/Even Using the GS4981
Odd/even field information can be derived using the vertical
and horizontal outputs from the GS4981 along with an external
positive edge D flip/flop. The horizontal output is used
as the D input and the vertical output as the clock, as
shown in Figure 27.
At the start of an odd field the vertical output ends in the middle
of the horizontal line and a high will be latched. At the start of
an even field, the vertical output ends near the beginning of
the horizontal line and since the horizontal output is low, a low
will be latched. This timing sequence is shown in Figure 28.
COMPOSITE
SYNC OUTPUT
COMPOSITE
VIDEO INPUT
VERTICAL
SYNC OUTPUT
0.1µF
GS4981
1
8
2
7
3
6
4
5
680kΩ
0.1µF
V_CC 5 - 12V
HORIZONTAL
R _SET
BACK PORCH
OUTPUT
D FLIP/FLOP
D
Q
CLK Q
ODD/EVEN
OUTPUT
START OF ODD FIELD
525
1
COMPOSITE
VIDEO INPUT
HORIZONTAL OUTPUT
GS4981
VERTICAL SYNC OUTPUT
GS4981
Fig. 27 Derivation of Odd/Even with GS4981
2
3
4
5
6
7
8
ODD/EVEN OUTPUT
START OF EVEN FIELD
263
264
COMPOSITE
VIDEO INPUT
HORIZONTAL
GS4981
VERTICAL SYNC OUTPUT
GS4981
265
266
267
268
269
270
ODD/EVEN OUTPUT
Fig. 28 Timing Diagram
REVISION NOTES
The only change from 520-23-02 to 520-23-03 is that the document has been
upgraded to a full DATA SHEET. It is no longer Preliminary.
DOCUMENT
IDENTIFICATION
PRODUCT PROPOSAL
This data has been compiled for market investigation purposes
only, and does not constitute an offer for sale.
ADVANCE INFORMATION NOTE
This product is in development phase and specifications are
subject to change without notice. Gennum reserves the right to
remove the product at any time. Listing the product does not
constitute an offer for sale.
PRELIMINARY
The product is in a preproduction phase and specifications are
subject to change without notice.
DATA SHEET
The product is in production. Gennum reserves the right to
make changes at any time to improve reliability, function or
design, in order to provide the best product possible.
Gennum Corporation assumes no responsibility for the use of any circuits described herein and makes no representations that they are free from patent infringement.
© Copyright March 1991 Gennum Corporation. All rights reserved. Printed in Canada.
520 - 23 - 03
14