LM1237BDBC/NA National Semiconductor, LM1237BDBC/NA Datasheet - Page 18

• Manufacturer Part Number: LM1237BDBC/NA
• Description: Video ICs, 150MHz I2C Compatible RGB Preamplifier with Internal 254 Character OSD and 4 DACs
• Manufacturer: National Semiconductor

www.national.com
OSD Generator Operation
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.
1. Button Boxes — The OSD generator examines the char-
2. Heavy Button Boxes — When heavy button boxes are
(of Previous
Character)
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
(‘highlight’) is defined by the value in the color palette
register, EF1 (normally white). The depressed pixel
(‘lowlight’) color by the value in the color palette register
EF2 (normally gray). See Figure 16.
selected, the color palette value stored in register EF3 is
CHAR1
Bit 0
2
C compatible interface. The raised pixel color
Bit 11
Effect on the screen:
RAISED
CHAR1
Bit 0
(Continued)
(of Character
FIGURE 16. Button Boxes
Line 0
Line 17
Below)
Line 0
20023452
18
(of Previous
Character)
3. Shadowing — Shadowing can be added to two-color
4. Bordering — A border can be added to the two-color
5. Blinking — If blinking is enabled as an attribute, all colors
Bit 0
CHAR1
used for the depressed (‘lowlight’) pixel color instead of
the value in register EF2.
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
register EF3 (normally black).
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).
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
interface.
Bit 11
DEPRESSED
CHAR1
20023424
Bit 0
2
(of Character
C compatible
Line 0
Line 17
Below)
Line 0
20023423