Black-And-White Operation - Freescale Semiconductor MCF52277 Reference Manual

Byte
Address
0
1
2
3
Byte
Address
0
1
2
3
21.4.5

Black-and-White Operation

The 1 bpp mode is also known as black-and-white mode because each pixel is always fully on or fully off.
21.4.6 Gray-Scale Operation
The LCDC generates a maximum of 16 gray levels. These gray levels are defined by 2 or 4 bits of display
data for each pixel. Using 2 bpp, the LCDC displays 4 shades of gray, and using 4 bpp, the LCDC displays
all 16 shades. The shades of gray are obtained by controlling the number of frames in which the pixel is
on over a period of 16 frames. This method is known as frame rate control (FRC). For more information
on FRC, see Section 21.4.8, "Frame Rate Modulation Control (FRC)
The use of the mapping RAM is shown in
one of four gray levels, and when using 4 bpp, the 4-bit code is mapped to one of 16 gray levels. Because
crystal formulations and driving voltages vary, the visual gray effect may or may not be linearly related to
the frame rate. A logarithmic scale such as 0, 1/4, 1/2 and 1 might be more pleasing than a linearly spaced
scale such as 0, 5/16, 11/16 and 1 for certain graphics.
Figure 21-32 illustrates gray-scale pixel generation. The flexible mapping scheme allows the user to
optimize the visual effect for a specific panel or application.
Freescale Semiconductor
Sample Bit-to-Pixel Mapping
Bit 7 Bit 6 Bit 5
Blue [5] Blue [4] Blue [3]
Bit 15 Bit 14 Bit 13
Green [5] Green [4] Green [3]
Bit 23 Bit 22 Bit 21
Red [5] Red [4] Red [3]
Bit 31 Bit 30 Bit 29
Microsoft PAL_BGR 18bpp Mode
Sample Bit-to-Pixel Mapping
Bit 7 Bit 6 Bit 5
Red [5] Red [4] Red [3]
Bit 15 Bit 14 Bit 13
Green [5] Green [4] Green [3]
Bit 23 Bit 22 Bit 21
Blue [5] Blue [4] Blue [3]
Bit 31 Bit 30 Bit 29
Figure 21-31. Display Data Mapping for 18 bpp Modes
Figure
MCF52277 Reference Manual, Rev. 1
18 bpp Mode
Bit 4 Bit 3 Bit 2
Blue [2] Blue [1] Blue [0]
Bit 12 Bit 11 Bit 10
Green [2] Green [1] Green [0]
Bit 20 Bit 19 Bit 18
Red [2] Red [1] Red [0]
Bit 28 Bit 27 Bit 26
Bit 4 Bit 3 Bit 2
Red [2] Red [1] Red [0]
Bit 12 Bit 11 Bit 10
Green [2] Green [1] Green [0]
Bit 20 Bit 19 Bit 18
Blue [2] Blue [1] Blue [0]
Bit 28 Bit 27 Bit 26
21-32. When using 2 bpp, the 2-bit code is mapped to
Liquid Crystal Display Controller (LCDC)
Bit 1 Bit 0
Bit 9 Bit 8
Bit 17 Bit 16
Bit 25 Bit 24
Bit 1 Bit 0
Bit 9 Bit 8
Bit 17 Bit 16
Bit 25 Bit 24
21-33