CHRONTEL

CH7002D

9

*Patent number 5,874,846

201-0000-029 Rev6.1, 8/2/99

Operating Modes (Continued)

Overscan/Underscan

The inclusion of both overscan and underscan forms of output display have been created to enable optimal use of the

CH7002 for different application needs. In general, underscan provides an image that is entirely viewable on screen.

It should be used as the default for most applications (e.g. viewing text screens, operating games, running

productivity applications, working within Windows). Overscan provides an image that bleeds past the edges of the

TV screen, exactly like normal television programs and movies appear on TV. It is only recommended for viewing

movies or video clips coming from the computer.

Anti-Flicker Filter

The CH7002 integrates a 3-line vertical filter circuit to help eliminate the flicker associated with interlaced displays.

When operating in underscan mode, this flicker circuit provides a adaptive filter algorithm for implementing flicker

reduction based on an approximate 1:2:1 weighting sequence. When operating in overscan mode, it provides four

(either 0:1:0 filtering or 1:2:1 filtering) when using direct pin programming mode.

Table 2. CH7002 Operating Modes

Name

PAL OUT

800x600 IN

PAL OUT

640x480 IN

Underscan

NTSC

640x480 IN

Overscan

NTSC OUT

640x480 IN

Underscan

PAL OUT

640x480 IN

Overscan

PAL OUT

800x600 IN

Overscan

NTSC OUT

800x600 IN

Underscan

Mode

0

1

2

3

4

5

6

Pixel

Clock

35.400

25.000

25.175

28.196

25.000

29.500

43.636

Scale

Factor

5/6

1/1

1/1

7/8

1/1

1/1

3/4

Total VGA

Lines

750

625

525

600

625

625

700

Active

VGA Lines

600

480

480

480

480

600

600

Fvert VGA

(Hz)

50.0

50.00

59.94

59.94

50.00

50.00

59.94

Fhor VGA

(KHz)

37.5

31.250

31.469

35.964

31.250

31.250

41.958

Total TV

Lines

625

625

525

525

625

625

525

Active TV

Lines

500

480

480

420

480

600

450

Fvert TV

(Hz)

50.00

50.00

59.94

59.94

50.00

50.00

59.94

Fhor TV

(Hz)

15625.0

15625.0

15734.3

15734.3

15625.0

15625.0

15734.3

Table 3. Anti-Flicker Filter Modes

FF0

FF1

Filter Modes

0

0

0:1:0 averaging (no filtering)

0

1

1:3:1 averaging

1

0

1:2:1 averaging

1

1

1:1:1 averaging