Motorola MPC823e Reference Manual page 1009

LCD Controller
18.3.2.2 COLOR. Each color pixel is represented as a 4- or 8-bit code in the frame buffer.
Using the color RAM, the pixel code is mapped to a 12-bit red/green/blue (RGB) code, which
allows you to select one of 4,096 colors. For passive color displays, the frame rate control
algorithm processes each color to generate the required amount of intensity, as derived from
the 12 bits (maximum) of RGB information in the color RAM. For active color displays,
12 bits (4 bits per color) are output directly onto the LCD data bus. Figure 18-9 illustrates
color generation. Notice that the LCD data bus is shown with MSB on the left and LSB on
the right. The LCD_A, LCD_B, and LCD_C bits are the least-significant bits of each color,
PASSIVE DISPLAY
DISPLAY DATA
0 1 1 0
DISPLAY DATA
0 0 0 0 0 1 1 0
G
R
0 1 1 1 1 1 1
FRC FRC
(RED) (GREEN) (BLUE)
* * *
LCD PIXEL
NOTE: * FOR EACH FRAME IN A GROUP OF 16, 1 INDICATES THIS COLOR PIXEL IS ON AND 0 INDICATES THIS COLOR PIXEL IS OFF.
18-12
FOUR BITS PER PIXEL
EIGHT BITS PER PIXEL
B
COLOR
RAM
1 1 0 0 0
(256 ENTRIES)
FRC
Figure 18-9. Color Generation
MPC823e REFERENCE MANUAL
ACTIVE DISPLAY
DISPLAY DATA
FOUR BITS PER PIXEL
0 1 1 0
DISPLAY DATA
EIGHT BITS PER PIXEL
0 0 0 0 0 1 1 0
G B
R
0 1 1 1 1 1 1 1 0 0 0
1
0 1 1 1 1 1 1 1 0 0 1 0
MOTOROLA