6 gray scaler, 7 upper and lower panel formatters, Nxp semiconductors – NXP Semiconductors LPC24XX UM10237 User Manual
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User manual
Rev. 04 — 26 August 2009
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NXP Semiconductors
UM10237
Chapter 12: LPC24XX LCD controller
Cursor pixel encoding
Each pixel of the cursor requires two bits of information. These are interpreted as Color0,
Color1, Transparent, and Transparent inverted.
In the coding scheme, bit 1 selects between color and transparent (AND mask) and bit 0
selects variant (XOR mask).
shows the pixel encoding bit assignments.
6.6 Gray scaler
A patented gray scale algorithm drives monochrome and color STN panels. This provides
15 gray scales for monochrome displays. For STN color displays, the three color
components (RGB) are gray scaled simultaneously. This results in 3375 (15x15x15)
colors being available. The gray scaler transforms each 4-bit gray value into a sequence
of activity-per-pixel over several frames, relying to some degree on the display
characteristics, to give the representation of gray scales and color.
6.7 Upper and lower panel formatters
Formatters are used in STN mode to convert the gray scaler output to a parallel format as
required by the display. For monochrome displays, this is either 4 or 8 bits wide, and for
color displays, it is 8 bits wide.
shows a color display driven with 2 2/3 pixels
worth of data in a repeating sequence.
5:4
(1, 0)
(17, 0)
(33, 0)
(49, 0)
(1, y)
(17, y)
(33, y)
(49, y)
(49, 63)
3:2
(2, 0)
(18, 0)
(34, 0)
(50, 0)
(2, y)
(18, y)
(34, y)
(50, y)
(50, 63)
1:0
(3, 0)
(19, 0)
(35, 0)
(51, 0)
(3, y)
(19, y)
(35, y)
(51, y)
(51, 63)
Table 256. Buffer to pixel mapping for 64 x 64 pixel cursor format
Offset into cursor memory
Data bits
0
4
8
12
(16 * y)
(16 * y) +4
(16 * y) + 8
(16 * y) + 12
FC
Table 257. Pixel encoding
Value
Description
00
Color0.
The cursor color is displayed according to the Red-Green-Blue (RGB) value
programmed into the CRSR_PAL0 register.
01
Color1.
The cursor color is displayed according to the RGB value programmed into the
CRSR_PAL1 register.
10
Transparent.
The cursor pixel is transparent, so is displayed unchanged. This enables the visible
cursor to assume shapes that are not square.
11
Transparent inverted.
The cursor pixel assumes the complementary color of the frame pixel that is displayed.
This can be used to ensure that the cursor is visible regardless of the color of the
frame buffer image.