Grayscale Algorithm - Sharp LH79524 User Manual

LH79524/LH79525 User's Guide Color Liquid Crystal Display Controller

4.3.6.1 Grayscale Algorithm

A patented grayscale algorithm drives the monochrome and color STN panels.
• For monochrome displays, the gray-scale algorithm provides 15 gray scales.
• For color displays, the 3-color components (red, green, and blue) are grayscaled simul-
taneously. This results in 3,375 colors (15 × 15 × 15) being available for Color STN Mode.
The grayscaler transforms each 4-bit gray value into a sequence of activity-per-pixel over
several frames, relying partially on the display characteristics to provide the representation
of gray scales and color.
Red, green, and blue pixel data bit values from the gray scaler are shifted concurrently into
the respective registers in the upper and lower panel formatter. When sufficient data is
available, a byte is constructed by assembling the data to the correct bit position for the
LCD panel's RGB data pattern.
4.3.6.2 Interrupts
The CLCDC has four individually maskable interrupt conditions associated with a single
combined interrupt. The single combined interrupt is asserted if any of the combined inter-
rupt conditions are asserted and unmasked.
4.3.6.3 LCD Panel Resolutions
LCD panel resolution is expressed as the total number of horizontal pixels multiplied by the
total number of vertical pixels. The CLCDC supports STN, TFT, HR-TFT, and AD-TFT
LCD panels. The only requirement for supporting these displays is for the width to be divis-
ible by 16; there is no limit on height. Examples of resolutions supported include:
• 160 × 120
• 320 × 200
• 320 × 240
• 640 × 200
• 640 × 240
• 640 × 480 8-bit (this resolution requires significant processor bandwidth)
TFT, HR-TFT, and AD-TFT LCD panels utilize color palette RAM. For these panels, each
16-bit palette entry is composed of 5 bpp, plus a common intensity bit. In addition, the total
number of supported colors can be doubled from 32,768 to 65,536 if the Intensity bit is uti-
lized and applied simultaneously to all three color components (R, G, and B).
Version 1.0 4-9