GM2121 Datasheet, PDF (35/51 Pages) List of Unclassifed Manufacturers – SXGA LCD Monitor Controller with Integrated Analog Interface and Dual LVDS Transmitter

gm2121 Preliminary Data Sheet
stored as 1-bit per pixel data, 2-bit per pixel data or 4-bit per pixel data. This permits a good compression
ratio while allowing more than 16 colors in the image.
Some general features of the gm2121 OSD controller include:
OSD Position – The OSD menu can be positioned anywhere on the display region. The reference point is
Horizontal and Vertical Display Background Start (DH_BKGND_START and DV_BKGND_START in
Figure 20).
OSD Stretch – The OSD image can be stretched horizontally and/or vertically by a factor of two, three,
or four. Pixel and line replication is used to stretch the image.
OSD Blending – Sixteen levels of blending are supported for the character-mapped and bitmapped
images. One host register controls the blend levels for pixels with LUT values of 128 and greater,
while another host register controls the blend levels for pixels with LUT values of 127 and lower.
OSD color LUT value 0 is reserved for transparency and is unaffected by the blend attribute.
4.13.1 On-Chip OSD SRAM
The on-chip static RAM (4096 words by 24 bits) stores the cell map and the cell definitions.
In memory, the cell map is organized as an array of words, each defining the attributes of one visible
character on the screen starting from upper left of the visible character array. These attributes specify
which character to display, whether it is stored as 1, 2 or 4 bits per pixel, the foreground and background
colors, blinking, etc.
Registers CELLMAP_XSZ and CELLMAP_YSZ are used to define the visible area of the OSD image.
For example, Figure 24 shows a cell map for which CELLMAP_XSZ =25 and CELLMAP_YSZ =10.
Address26:
Cell attributes for
1^st cell, 2^nd row
Address 1:
Cell Attributes for
upper-left hand cell
CELLMAP_XSZ
Address 25:
Attributes for
upper-right hand cell
CELLMAP_YS
Z
Brightness
Contrast
Figure 24.
OSD Cell Map
Cell definitions are stored as bit map data. On-chip registers point to the start of 1-bit per pixel
definitions, 2-bit per pixel definitions and 4-bit per pixel definitions respectively. 1, 2 and 4-bit per pixel
cell definitions require 9, 18 and 36 words of the OSD RAM respectively.
C2121-DAT-01F
35
http://www.genesis-microchip.com
December 2002