MB87P2020 Datasheet, PDF (156/356 Pages) Fujitsu Component Limited. – Colour LCD/CRT/TV Controller

MB87J2120, MB87P2020-A Hardware Manual
2 Color Space Concept
2.1 Background
The GDC-ASIC allows to use several numbers of bits per pixel to represent pictures in its VideoRAM (1,
2, 4, 8, 16, and 24 bits per pixel). They may even be different in different planes. The color¹ space defined
by these bits shall be referred to as logical color space.
Actual displays, however, might have color resolutions differing from those in the logical space. The
number of bits per pixel as supported by the display actually wired to the GDC-ASIC shall be referred to as
physical color space.
Obviously, there is the need to map the logical onto the physical color space. Additional internal units such
as a Color Look-up Table (CLUT), a YUV to RGB Matrix (Jasmine only), and a Duty Ratio Modulator
(DRM) lead to another internal representation which shall be referred to as intermediate color space. This
internal representation is laid out as to provide some kind of common ground between logical and physical
color space.
2.2 Data Flow for Color Space Conversion within GPU
Figure 2-1 gives an overview on the logical data flow for color space conversion. This does not represent
actual GPU-pipeline stages but conceptual fields where the different color spaces apply.
Video
RAM
CLUT
DRM
BSF
YUV
Matrix
GTab
Logical
Color Space
Intermediate
Color Space
Physical
Color Space
Figure 2-1: Basic data flow for color space conversion.
DAC
Display
Display Interface Signals
Pixel data held in VideoRAM belongs to logical color space. It is mapped to intermediate color space
through one of the ways listed in Table 2-1. Mapping to physical color space is carried out according to
Table 2-2. Signals actually wired to the physical display are interpreted in this physical color space. How-
ever, there is one additional stage of conversion: bit stream formatting. Displays may require data in a
stream with bit groups not necessarily equal to one pixel. Therefore, an appropriate postprocessing is indis-
pensable (see 1.2.5 and 3.3).
1. “color” here refers to different hues as well as to different shades of monochrome
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