PXD20RM Datasheet, PDF (535/1628 Pages) Freescale Semiconductor, Inc – PXD20 Microcontroller

which determine the location of the upper left pixel of the layer in the x and y axes. Both fields are
expressed in terms of the number of pixels in each axis.
There are no restrictions on layer placement. Any layer can be placed and moved to any panel position. If
a layer is placed so that pixels would appear beyond the dimensions of the panel, then the DCULite
displays the pixels on the panel and ignores the pixels off the panel.
12.4.4.4 Graphics and data format
The memory location of the graphic that is displayed on the layer is defined by register 3 in the control
descriptor for the layer (CTRLDESCLn_3, where n is the layer number). This 32-bit value can contain the
address of any 64-bit aligned memory location in the memory map of the MCU.
The format of the data that describes the graphic is defined by the BPP bit field in register 4 in the control
descriptor for the layer (CTRLDESCLn_4, where n is the layer number). This value also influences the
range of values for the width of the layer (see Section 12.4.4.3, Layer size and positioning). By choosing
an appropriate format, it is possible to optimize the memory required by the graphics in use.
There are five formats where the RGB values of the pixels are stored directly in the graphic. In these
formats, the DCULite treats the data as describing a true RGB color. The formats are:
• BGRA8888, where the data defines 8-bit values for the red, green, blue, and alpha components of
the image. This blends as ARGB, however, in this format the order of the bytes is reversed
compared to other formats.
• RGB888, where the data defines 8-bit values for the red, green, and blue components of the image.
• RGB565 where the data defines 5-bit values for the red and blue components, and 6-bit values for
the green component of the image.
• 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).
Freescale Semiconductor
PXD20 Microcontroller Reference Manual, Rev. 1
Preliminary—Subject to Change Without Notice
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