Cirrus Logic EP93xx - Manual (Page 269)

DS785UM1 8-5
Copyright 2007 Cirrus Logic
Graphics Accelerator
EP93xx User’s Guide
8
8
8
8.4.1 Memory Organization for 1 Bit Per Pixel (bpp)
The 1 bpp storage format is for storing compressed image data for remapping only. This data
cannot be displayed until it is remapped into a supported color depth.
Table 8-2 shows how
compressed 1 bpp images are stored in memory as 8 pixels per byte.
8.4.2 Memory Organization for 4-Bits Per Pixel
The 4 bpp storage format can be used to support monochrome, 8 levels of grayscale, and 8
or 16 color displays. The actual frame buffer can be organized as 2 pixels per byte or 1 pixel
per byte. The Graphics Accelerator engine treats 4 bpp with 1 pixel per byte as 8 bpp mode.
Table 8-3 shows how 4 bpp images are stored in memory as 2 pixels per byte.
8.4.3 Memory Organization for 8-Bits Per Pixel
The 8 bpp storage format can be used to support 8 level grayscale and color displays. For
color displays, this mode would use a software changeable palette in the Raster Engine to
map 256 color selections to 24-bit colors.
Table 8-4 shows how 8 bpp images are stored in
memory as 1 pixel per byte.
Table 8-2. bpp Memory Organization
31 24 23 16 15 8 7 0
0x0000 P(7,3)....... ......P(0,3) P(7,2)....... ......P(0,2) P(7,1)....... ......P(0,1) P(7,0)....... ......P(0,0)
0x0004 X X X X P(7,5)....... ......P(0,5) P(7,4)....... ......P(0,4)
Table 8-3. 4 bpp Memory Organization
31 28 27 24 23 20 19 16 15 12 11 8 7 4 3 0
0x0000 P(6,0) P(7,0) P(4,0) P(5,0) P(2,0) P(3,0) P(0,0) P(1,0)
0x0004 P(6,1) P(7,1) P(4,1) P(5,1) P(2,1) P(3,1) P(0,1) P(1,1)
0x0008 P(6,2) P(7,2) P(4,2) P(5,2) P(2,2) P(3,2) P(0,2) P(1,2)
0x0000 P(6,3) P(7,3) P(4,3) P(5,3) P(2,3) P(3,3) P(0,3) P(1,3)
0x0004 P(6,4) P(7,4) P(4,4) P(5,4) P(2,4) P(3,4) P(0,4) P(1,4)
0x0008 P(6,5) P(7,5) P(4,5) P(5,5) P(2,5) P(3,5) P(0,5) P(1,5)