PXD20RM Datasheet, PDF (419/1628 Pages) Freescale Semiconductor, Inc – PXD20 Microcontroller

• ARGB1555 where the data defines 5-bit values for the red, green, and blue components, and a 1-bit
value for the alpha channel of the image.
• ARGB4444, where the data defines 4-bit values for the red, green, blue, and alpha components of
the image.
The three 16-bit formats (RGB565, ARGB1555, and ARGB4444) are promoted to full 8 bit per
component format by shifting the bits left so that the MSB of the component in the 16-bit format becomes
the MSB of the 24/32 bpp (bit per pixel) format, and the LSB is filled with the value of the MSBs. For
example, an RGB565 value of 10000:010000:11011 becomes 10000100:01000001:11011110. An
RGB4444 value of 1010:0011:1100:0101 becomes 10101010:00110011:11001100:01010101. An
RGB1555 value of 1:10100:01000:11011 becomes 11111111:10100101:01000010:11011110.
There are five indexed color formats (1/2/4/8 bpp & APAL8) where the data in the graphic does not define
the RGB color to display. Instead, the data defines the entry in a color look-up table (CLUT) that contains
a palette of ARGB colors. The maximum number of colors in the CLUT is defined by the size of the data
stored in the graphic. For 1 bpp graphics, there is a maximum of two colors in the CLUT. For 2 bpp, there
is a maximum of four colors. For 4 bpp and 8 bpp data, the maximums are 16 and 256 colors, respectively.
In APAL8 mode(16 bpp), the upper 8 bits define the alpha component of the pixel and the lower 8 bits
define the offset in the CLUT (the alpha component in the CLUT color is ignored).
The address of the first value in the CLUT is defined in the LUOFFS bit field of register 4 and the CLUT
is the RAM block dedicated to the DCU3 which is described in Section 11.4.6, CLUT/tile RAM. Since the
ARGB values stored in the CLUT are 32-bit ARGB, there is no need for further adjustment before
blending.
The DCU3 also supports graphics encoded using luminance and chrominance format. This format is
generically known as YUV and stores the luminance (brightness, Y) of a pixel separate from its
chrominance (color information, U and V). This format is widely used by cameras and is supported by the
PDI for direct video in as well as the DCU3 when stored in memory for display on a layer. The specific
implementation used by the DCU3 is more accurately described as YCbCr422 which uses twice as many
bits to describe the luminance as to describe the blue (Cb) and red (Cr) difference of the chrominance.
The DCU3 takes these pixels and converts them to RGB format using equations configured using its
LYR_LUMA_COMP, LYR_CHROMA_RED, LYR_CHROMA_GREEN, and LYR_CHROMA_BLUE
registers. The YCbCr format specifies a common chroma setting for two pixels; however, it is possible to
interpolate the chroma for the pixels rather than setting both to the same value. This feature is enabled by
the LYR_INTPOL_EN[EN] field. Due to the additional conversion step required, the DCU3 is able to
blend a maximum of one layer encoded in YCbCr for each pixel. See Section 11.8.1.6.3, PDI YCbCr mode
and DCU3 YCbCr color format.
There are four additional formats defined by the BPP bit field. These configure the graphic in transparency
mode and luminance mode (see Section 11.4.4.6, Transparency mode and blending, and Section 11.4.4.7,
Luminance mode, respectively).
There is a set storage format for each data format provided by the DCU3. These formats can be seen in
Table 11-60 to Table 11-70.
Freescale Semiconductor
PXD20 Microcontroller Reference Manual, Rev. 1
Preliminary—Subject to Change Without Notice
11-85