STV3550 datasheet(43/144 Pages) STMICROELECTRONICS

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Graphics Functional Description

STV3550

43/144

Color Characteristics

The address in the OSD Color Look-Up-Table (CLUT) (not in the SDRAM), where the color

defined in the palette of the current specification and pointed to by Palettep[31:0] will be loaded, is

defined in bits CLUTAdd[7:0]. If the New Palette bit is reset, these bits are ignored.

The number of colors which will be loaded in the OSD CLUT is defined in bits NCL[7:0]. The OSD

CLUT can contain up to 256 colors. For more information, refer to Section 4.1.4.2: Color Data on

page 46

Note:

When NCL[7:0] = 00h, one color will be loaded.

Each region may have its own palette, with its own number of colors (these colors will be loaded in

the OSD CLUT before displaying the bitmap). If a sequence of regions uses the same palette, the

palette need only be defined in the first region of the sequence. If a region only uses a part of the

colors defined in the palette of the previous region, the unused colors from the previous palette can

be reprogrammed for the current region in the OSD CLUT.

Mixing Characteristics

Four different modes may be applied to RGB components for mixing OSD and video signals: Pixel

Mixing mode, Global Mixing mode (mixing factor defined in Mix-Weight bits), Proportional

Mixing mode (mixing factor defined in Mix-Gain bits) and No Mixing mode (full OSD). The mixing

mode is specified in bits MiMo[1:0]. For more information, refer to Section 4.1.5: Mixing OSD and Video

Signals on page 48

Filter Mode

Flicker problems may occur inside an OSD when there is a significant difference in the color

between pixels in a top line and those of its surrounding bottom lines (e.g. if one object is visible in

one line and not in its surrounding lines).

Figure 32: OSD Region Positions

TV Screen

Y_top

Y_Bottom

X_right

X_left

Hsync

OSD Region

N Pixel Clock Periods

Horizontal Shift

Vsync

Vertical Shift “X” TV lines

N’ TV lines

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