SDA6000 Datasheet, PDF (291/380 Pages) Infineon Technologies AG – Teletext Decoder with Embedded 16-bit Controller

SDA 6000
Display Generator
10.3.1 Overlapped Layers
In overlapped layer mode the pixel information of both layers (layer 1, layer 2) is read in
parallel to the RAM. This means that for each pixel the individual decision can be made
which pixel source (layer 1, layer 2, screen background or video) has the highest priority.
Layer 2
Layer 1
Background Color
Video
UEA11172
Figure 10-3 Priority of Layers in Overlapped Layer Mode
The transparency between layers is supported. Below layer 2 there is layer 1, below
layer 1 there is the screen background colour and below screen background there is
video. In overlapped layer mode a transparency hierarchy is defined for layer 2, layer 1,
screen background and video. The transparency hierarchy is controlled, for each pixel,
by two bits (TR1 … 0) which are defined in the pixel format of the framebuffer and bit
SBTL which is defined in instruction SAR. Thus each pixel position can be defined
individually as layer 1, layer 2, screen background, video or contrast reduced video.
Depending on the transparency bits of both layers, subsequent signals are switched to
the RGB, COR and BLANK (normal polarity assumed) outputs of M2. As a result one of
the two layers or the screen background will be visible on the screen. If layer 2 is not
available for a pixel, signals COR, BLANK and RGB output depends on layer 1 only.
Users Manual
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2000-06-15