CH7006C datasheet(13/49 Pages) ETC

13 / 49 page

201-0000-026 Rev 2.1, 8/2/99

CHRONTEL

CH7006C

Display Modes (continued)

t is disigned to support output to either NTSC or PAL television formats. The CH7005 provides interpolated scaling

with selectable factors of 5:4, 1:1, 7:8, 5:6, 3:4 and 7:10 in order to support adjustable overscan or underscan

operation when displayed on a TV. This combination of factors results in a matrix of useful operating modes which

are listed in detail in Table 10.

(1) Note:Percent underscan is a calculated value based on average viewable lines on each TV format, assuming an average TV over-

scan

of 10%. (Negative values) indicate modes which are operating in underscan.

For NTSC: 480 active lines - 10% (overscan) = 432 viewable lines (average)

For PAL:

576 active lines - 10% (overscan) = 518 viewable lines (average)

The inclusion of multiple levels of scaling for each resolution have been created to enable optimal use of the

CH7006 for different application needs. In general, underscan (modes where percent overscan is negative provides

an image that is viewable in its entirety on screen; it should be used as the default for most applications (e.g.,

viewing text screens, operating games, running productivity applications and working within Windows).

Overscanning provides an image that extends past the edges of the TV screen, exactly like normal television

programs and movies appear on TV, and is only recommended for viewing movies or video clips coming from the

computer. In addition to the above mode table, the CH7006 also support interlaced input modes, both in CCIR 656

and proprietary formats (see Display Mode Register section.)

Flicker Filter and Text Enhancement

The CH7006 integrates an advanced 2-line, 3-line, 4-line and 5-line (depending on mode) vertical deflickering filter

circuit to help eliminate the flicker associated with interlaced displays. This flicker circuit provides an adaptive

filter algorithm for implementing flicker reduction with selections of high, medium or low flicker content for both

luma and chroma channels (see register descriptions). In addition, a special text enhancement circuit incorporates

Table 10. CH7006 Display Modes

TV Format

Standard

Input

(active)

Resolution

Scale

Factor

Active

TV Lines

Percent (1)

Overscan

Pixel

Clock

Horizontal

Total

Vertical

Total

NTSC

640x480

1:1

480

10%

24.671

784

525

NTSC

640x480

7:8

420

(3%)

28.196

784

600

NTSC

640x480

5:6

400

(8%)

30.210

800

630

NTSC

800x600

5:6

500

16%

39.273

1040

630

NTSC

800x600

3:4

450

43.636

1040

700

NTSC

800x600

7:10

420

(3%)

47.832

1064

750

NTSC

640x400

5:4

500

16%

21.147

840

420

NTSC

640x400

1:1

400

(8%)

26.434

840

525

NTSC

640x400

7:8

350

(19%)

30.210

840

600

NTSC

720x400

5:4

500

16%

23.790

945

420

NTSC

720x400

1:1

400

(8%)

29.455

936

525

NTSC

512x384

5:4

480

10%

20.140

800

420

NTSC

512x384

1:1

384

(11%)

24.671

784

525

PAL

640x480

5:4

600

14%

21.000

840

500

PAL

640x480

1:1

480

(8%)

26.250

840

625

PAL

640x480

5:6

400

(29%)

31.500

840

750

PAL

800x600

1:1

600

14%

29.500

944

625

PAL

800x600

5:6

500

(4%)

36.000

960

750

PAL

800x600

3:4

450

(15%)

39.000

936

836

PAL

640x400

5:4

500

(4%)

25.000

1000

500

PAL

640x400

1:1

400

(29%)

31.500

1008

625

PAL

720x400

5:4

500

(4%)

28.125

1125

500

PAL

720x400

1:1

400

(29%)

34.875

1116

625

PAL

512x384

5:4

480

(8%)

21.000

840

500

PAL

512x384

1:1

384

(35%)

26.250

840

625

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