LM1237AAFSLASHNA datasheet(18/42 Pages) NSC

18 / 42 page

OSD Generator Operation (Continued)

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

(‘lowlight’) color by the value in the color palette register

EF2 (normally gray). See Figure 16.

Heavy Button Boxes — When heavy button boxes are

selected, the color palette value stored in register EF3 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 2 image, as shown in Figure 17. 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 1 and color 2. See Figure 18. 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 1

and then back to the correct color at a rate determined

by the microcontroller through the I

2C compatible

interface.

RAISED

CHAR1

Bit 0

(of Previous

Character)

Line 0

(of Character

Below)

Bit 11

Bit 0

Line 0

Line 17

20023452

DEPRESSED

CHAR1

Bit 0

(of Previous

Character)

Line 0

(of Character

Below)

Bit 11

Bit 0

Line 0

Line 17

20023423

Effect on the screen:

20023424

FIGURE 16. Button Boxes

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