MB86290A Datasheet, PDF (50/184 Pages) Fujitsu Component Limited. – Graphics Controller Hardware Specifications

5.3 Display Color
Either direct color mode (16 bits/pixel) or indirect color mode (8 bits/pixel)
can be used for the C, M, and B layers. Only the direct color mode can be
used for the W layer.
5.3.1 Color Look-up Table
MB86290A has two color look-up tables (pallets) for the indirect color mode.
Each pallet has 256 entries. A color data item contains 18 bits of data (RGB
6 bit, respectively), which is correlated to each color code specified in 8-bit
data. Therefore, each pallet can show 256 colors at one time out of 262,144
color selections.
C-layer palette
This pallet is dedicated to the C layer and hardware cursors. If the overlay
blend mode is used, an alpha bit must be set at each color data. When this
alpha bit is set to 1, color blending between the C-layer pixel and W/M/B
layer pixels is performed according to the priority order specified in the
overlay section. This blending option cannot be used for the hardware
cursor.
M/B-layer palette
This pallet is shared by the M and B layers. If both the M and B layers are
set to the indirect color mode, they share this same color pallet.
5.3.2 Chroma-key Operation
MB86290A performs superimpose using the chroma-key function. When the
key color of this chroma-key operation matches the color of the C layer
during the display scan period, the GV signal output becomes L level. The
graphics signal output from MB86290A and the external video signal can be
switched by using this signal.
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