VII LCD CONTROLLER BLOCK: LCD CONTROLLER
Color-mode look-up tables
In color mode, the LCD controller uses the red (R), green (G), and blue (B) look-up tables. Each color element is represented by 4-bit data. RGB = 000 is black, RGB = F00 is red, RGB = 080 is 50% luminance green, RGB = F0F is magenta, RGB = FFF is white, and so on. In this way, colors are determined by the proportions of the three color elements. If the luminance of each color element is represented by 4 bits, then we obtain 16 ⋅ 16 ⋅ 16 = 4,096 colors. Of these, select as many pieces of color data as can be used for the available display mode (2, 4, 16, or 256 colors), and write them to the valid entries of the look-up tables before using the LCD panel.
In personal-computer applications, the luminance of each color element is generally represented by 8 bits (0x00 to 0xFF). To set up the LCD panel by referring to those colors, write the 4 high-order bits of that data to the look-up tables.
The differences in configurations between display modes are shown below.
(1)1-bpp (2-color) mode
Use the first two entries of each look-up table. Select 2-color data from among the 4,096 colors, and write it to the respective entries. The RGB data in entry 0 is output for pixel data "0", and the RGB data in entry 1 is output for pixel data "1". For monochrome display, write 0x0 to entry 0 and 0xF to entry 1 in each of the red, green, and blue look-up tables before using the LCD panel.
| | | | | Index | Red look-up table | | | |
1-bit pixel data "0" | | | | | 0 | 4-bit R data for pixel data "0" | | | 4-bit R display data |
| | |
| | | | | | | |
"1" | | | | | 1 | 4-bit R data for pixel data "1" | | | |
| | | | | |
| | | 2 | | | | |
| | | : | Unused | | | |
| | | 15 | | | | |
| | | | | Index | Green look-up table | | | |
| | | | | 0 | 4-bit G data for pixel data "0" | | | 4-bit G display data |
| | | | |
| | | | | 1 | 4-bit G data for pixel data "1" | | |
| | | | | | | |
| | | 2 | | | | |
| | | : | Unused | | | |
| | | 15 | | | | |
| | | | | Index | Blue look-up table | | | |
| | | | | 0 | 4-bit B data for pixel data "0" | | | 4-bit B display data |
| | | | |
| | | | | 1 | 4-bit B data for pixel data "1" | | |
| | | | | | |
| 2 | | | | |
| : | Unused | | | |
| 15 | | | | |
Figure 2.12 Look-up Table in 1-bpp (2-Color) Mode
Table 2.9 shows an example of the basic data setting.
Table 2.9 Example of Look-up-Table Settings in 1-bpp (2-Color) Mode
Index | R look-up table | G look-up table | B look-up table |
0 | 0 | 0 | 0 |
1 | 0xF | 0xF | 0xF |
2–15 | 0 | 0 | 0 |
