LM2467 datasheet(22/43 Pages) NSC

22 / 43 page

OSD Generator Operation (Continued)

OSD WINDOW FADE IN/ FADE OUT

The OSD window can be opened and closed with a fade

in/fade out effect. The interval for fading in and fading out the

OSD window in the horizontal and vertical direction is vari-

able and can be set by the microcontroller. This allows the

OSD window to be opened or closed in the vertical direc-

tions, horizontal direction, or from the upper left to lower right

corner. Assuming the desired time to typically complete a full

fade in or fade out is 0.5 seconds, and if the vertical scan

frequency is for example, 60 Hz, the number of steps is:

With a typical OSD window that is 300 pixels wide and 180

video lines long, the horizontal and vertical intervals would

be:

For a smooth fade in or fade out animation from the upper

left corner to the lower right corner, the horizontal to vertical

interval ratio must be matched to the aspect ratio of the OSD

window. In the example above, the 300 pixel wide by 180

lines long OSD window has an aspect ratio of 5:3. Thus, the

horizontal to vertical interval ratio should be set to 5/3 or

10/6. With an OSD window aspect ratio of 3:2, the H/V

intervals can be set to 3/2, 6/4, 9/6, 12/8, or 15/10 for optimal

operation. If the calculated aspect ratio of an OSD window is

a non-integer ratio, the H/V interval ratio should meet or

exceed the aspect ratio. For example, if the OSD aspect

ratio is 3.7:2 (or 1.85:1), the H/V intervals should be set to

2/1, 4/2, 6/3, 8/4, 10/5, or 12/6. The fade in/out speed

increases as H/V interval settings are increased. The OSD

window can also be faded in or out in only one direction if

desired, by setting the horizontal interval to 0 for fading in/out

strictly in the vertical direction or setting the vertical interval

to 0 for fading in/out in the horizontal direction. In interlaced

video formats, it is not recommended to fade in and fade out

the OSD in the vertical direction, and should be only faded in

the horizontal direction. The fade in/out function can be

enabled/disabled with bit 5 of the frame control register,

0x8400, and the horizontal & vertical intervals are controlled

by setting register 0x8429. The OSD window fade in/out

feature can only be used with OSD window 1.

ENHANCED FEATURES

In addition to the wide selection of colors for each character,

additional character features can be selected on a character

by character basis. There are 3 Enhanced Feature Regis-

ters, EF0, EF1 and EF2.

Button Boxes — The OSD generator examines the char-

acter string being displayed and if the “button box” at-

tributes have been set in the Enhanced feature byte,

then a box creator selectively substitutes the character

pixels in either or both the top and left most pixel line or

column with a button box pixel. The shade of the button

box pixel depends upon whether a “depressed” or

“raised” box is required, and can be programmed

through the I

2C compatible interface. The raised pixel

color (“highlight”) is defined by the value in the color

palette register, EF1 (0x8405–0x8406), which is nor-

mally set to white. The depressed pixel (“lowlight”) color

by the value in the color palette register, EF2

(0x8407–0x8408), which is normally set to gray. See

Figure 19 for detail and Figure 20 for the on-screen

effect.

Heavy Button Boxes — When heavy button boxes are

selected, the color palette value stored in register EF3

(0x8409 - 0x840A) is used for the depressed (“lowlight”)

pixel color instead of the value in register EF2.

Shadowing — Shadowing can be added to two-color

characters by choosing the appropriate attribute value

for the character. When a character is shadowed, a

shadow pixel is added to the lower right edges of the

color 1 image, as shown in Figure 21. The color of the

shadow is determined by the value in the color palette

Bordering — A border can be added to the two-color

characters. When a character is bordered, a border pixel

is added at every horizontal, vertical or diagonal transi-

tion between color 0 and color 1. See Figure 22. The

color of the border is determined by the value in the color

palette register EF3 (normally black).

Blinking — If blinking is enabled as an attribute, all colors

within the character except the button box pixels which

have been overwritten will alternately switch to color 0

and then back to the correct color at a rate determined

by the microcontroller through the I

2C compatible

interface.

LM2467 数据表(PDF) 22 Page - National Semiconductor (TI)

LM2467 数据表(HTML) 22 Page - National Semiconductor (TI)

Html Pages

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43

数据表下载