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7-12 Intel® PXA26x Processor Family Developer’s Manual
Liquid Crystal Display Controller
7.4.2 External-Frame Buffer
The external frame buffer is an off-chip memory area used to supply enough encoded pixel values to fill
the entire screen one or more times. The number of pixel data values depends on the size of the
screen (for example, 640x480=307,200 encoded pixel values). Figure 7-6 through Figure 7-18
show the memory organization within the frame buffer for each size pixel encoding.
In the following figures, base refers to the initial address programmed in FSADR, palette buffer
index refers to the data that specifies the location in the palette buffer, and raw pixel data refers to
the actual 16-bit RGB data when the palette RAM is bypassed.
Figure 7-5. Palette-Buffer Format
Individual Palette Entry
Bit1514131211109876543210
Color Red (R) Green (G) Blue (B)
Bit1514131211109876543210
Mono unused Monochrome (M)
Little Endian Palette Entry Ordering
4-, 16- or 256-Entry Palette Buffer
Bit 31 16 15 0
Base
+ 0x0
Palette entry 1 Palette entry 0
Base
+ 0x4
Palette entry 3 Palette entry 2
Entries 4 through 255 do not exist for 1 and 2
bits/pixel.
Base
+
0x1C
Palette entry 15 Palette entry 14
Base
+
0x20
Palette entry 17 Palette entry 16
Entries 16 through 255 do not exist for 1,
2, and 4 bits/pixel.
Base
+
0x1F
C
Palette entry 255 Palette entry 254
Figure 7-6. 1-Bit Per Pixel Data Memory Organization
Bit 0
1 bit/pixel Palette Buffer Index[0]