STV3550 datasheet(47/144 Pages) STMICROELECTRONICS

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Graphics Functional Description

STV3550

47/144

Note:

Due to the GAMMA specification, the Alpha[7:0] range is from 0 to 128 in decimal (00h is

transparent, 80h is full OSD). All values greater than 80h (from 81h to FFh) are clamped to 80h.

The user may define a color palette with “n” number of colors (“n” words of 32 bits) for a single OSD

region. Before this region is displayed, these colors are loaded into a Color Look Up Table (CLUT)

in SDRAM where the RGB and Alpha bits are written.

The user defines the number of colors that will be loaded into the CLUT (NCL[7:0]) and the address

in the CLUT where the first color will be loaded (CLUTAdd[7:0]). These two parameters may be used

to reprogram or modify certain colors in the CLUT when several regions are displayed

simultaneously.

Note:

Palettep[31:0]

points to the address in SDRAM of the first byte of the first color loaded.

CLUTAdd[7:0] is only used to load the colors in the CLUT and not to read the CLUT during display.

The number of colors in the palette (programmed in the SDRAM) can be greater or less than 256 (a

color is a word of 32 bits). But, a only maximum of 256 colors will be loaded in the OSD CLUT.

The NCL[7:0] parameter refers to a contiguous number of colors programmed in the palette. If

NCL = 0, one color will be loaded.

Each OSD specification after the first one can either use the same color palette as the previous

OSD region, or a new one can be defined. If a new palette is defined in the SDRAM, the following

bits must be modified in the header:

●

must be set.

●

Palettep[31:0]

will indicate the new address of the first byte to be loaded.

●

NCL[7:0]

gives the number of colors to be loaded in the OSD CLUT.

●

CLUTAdd[7:0]

gives the OSD CLUT address where the first color will be loaded.

CLUT outputs are 32-bits; 8-bits for R, 8-bits for G, 8-bits for B, plus 8 bits for transparency control

(or mixing factor).

4.1.4.3 OSD Bitmap

The bitmap defines the OSD pixels, from left to right, in order and within lines, and follows the lines

from top to bottom. The first line of a bitmap is always a top line, and the last line is always a bottom

line. The number of bits per pixel is 8. The value for each pixel gives the line of the palette or the

address in the CLUT, which defines the color for the pixel.

The bitmap block is subdivided in two field blocks, the top field block and the bottom field block.

These two blocks always contain the same number of pixels (in both Interlaced and Progressive

mode). Each field block (top or bottom) defines one field of one region and each block must be

contiguous, aligned on a 32-bit boundary in the SDRAM.

Alpha[7:0]

Alpha Pixel Mixing factor

Values greater than 80h are clamped to 80h.

00h:

80h:

31 30 29 28 27 26 25 24 23 22 21 20 19 18 17 16 15 14 13 12 11 10

987

6543

210

Pixel 4

+1 Pixel

Pixel 1

Pixel 8

+1 Pixel

Pixel 5

Table 12: : Palette Line Format in 32-bit Color

Bitfield

Bits

Description

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