PXD10RM Datasheet, PDF (425/1332 Pages) Freescale Semiconductor, Inc – PXD10 Microcontroller

Figure 12-73. Case 6 example (only foreground color blended)
12.4.5.7 Luminance mode
Luminance mode is a special case for the graphic data format and 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 12.4.5.3, Layer size and
positioning”). By choosing an appropriate format, it is possible to optimize the memory required by the
graphics in use.
In luminance mode, the data in the source graphic does not contain any direct or indexed color information
or alpha information. The data values in a layer in luminance mode modify the values of the pixels on
underlying layers only. There are two luminance modes available: 4 bpp and 8 bpp. In both cases, the data
values behave as signed integers that are added to each component of the underlying pixel. The 4 bpp mode
is left-shifted to form a signed 8 bpp integer. The results of the addition are prevented from overflowing,
so that any result greater than 0xFF is set to 0xFF and any result less than 0x00 is set to 0x00.
The result of a blend with a luminance layer is that the intensity of the underlying pixel's color will be
increased or decreased. In this way, luminance mode can be used to highlight or dim pixels on the panel
without having to modify the source graphic data. Table 12-64 describes the effect of luminance blends on
an underlying pixel.
Table 12-64. Example of a blend with a luminance mode layer
Pixel value
0xFF8040
0xFF8040
Luminance value
0x40
0xC0
Resultant pixel
0xFFC080
0x3F0000
12.4.5.8 Tile mode
Tile mode is a special case for the layer and is enabled by the TILE_EN bit field in register 4 in the control
descriptor for the layer (CTRLDESCLn_4, where n is the layer number).
In this mode the layer size register (CTRLDESCLn_1, where n is the layer number) defines the size of the
layer; however, the size of the graphic is defined in control register 7 (CTRLDESCLn_7, where n is the
Freescale Semiconductor
PXD10 Microcontroller Reference Manual, Rev. 1
Preliminary—Subject to Change Without Notice
12-93