
HD66766R Rev. 1.0-1 / September 2002
58
Grayscale Palette
The HD66766R incorporates a grayscale palette to simultaneously display 65K of the 140,608 possible
colors. The grayscales consist of 32 6-bit palettes. The 52-stage grayscale levels can be selected from
the 6-bit palette data.
For the display data, the four-bit data in the GRAM written from the microcomputer is used.
In this palette, a pulse-width control system (PWM) is used to eliminate flicker in the LCD display. The
time over which the LCDs are switched on is adjusted according to the level and grayscales are displayed
so that flicker is reduced and grayscales are clearly displayed.
Figure 44Grayscale Palette Control
Display data
SB
LSB
Graphic RAM ( GRAM )
5
R2
R1
R0
R3
R4
G2
G1
G0
G3
G4
G5
B1
B0
B3
B2
B4
6
5
52 gray scale control
<R>
52 gray scale control
<G>
5
6
5
LCD Driver
R
G
B
32
64 gray scale
32
32
5
52 gray scale control
<B>
LCD Driver
LCD Driver
32
64
<RGB>
Palette
Palette register
Initialized value
PK0 (5
0
PK1 (5
0)
0
0)
0
0
0
0
0
0
0
1
1
1
1
0
0
0
0
0
1
0
0
0
0
0
1
0
1
0
0
0
1
1
0
0
0
0
1
1
0
0
0
1
1
1
1
0
1
0
0
0
0
0
1
0
0
1
"00000"
"00001"
"00010"
"00011"
"00100"
"00101"
"00110"
"00111"
"01000"
"01001"
"01010"
0
1
0
0
1
PK2 (5
0)
PK3 (5
0)
PK4 (5
0)
PK5 (5
0)
PK6(5
0)
PK7 (5
0)
PK8 (5
0)
PK9 (5
0)
PK10 (5
0)
0
1
1
0
0
0
1
0
0
1
1
0
1
0
PK15 (5
1
1
0
0
1
0
PK16 (5
1
1
1
1
0
0)
0
0
0
1
PK18 (5
0
0
0
1
1
1
0
0
1
1
0
0
0
1
1
1
1
0
1
1
0
0
1
0
1
1
0
1
PK11 (5
0)
01100
"01011"
"01110"
"01111"
"10000"
"10001"
"10010"
"10011"
"10100"
"10101"
"01101"
0
1
0
1
0
0
PK12 (5
0)
PK13 (5
0)
PK14 (5
0)
0)
0)
PK17(5
0)
PK19 (5
0)
PK20 (5
0)
PK21 (5
0)
0
1
1
1
0
0
0
1
1
1
0
0
1
0
0
0
0
1
1
0
1
1
1
1
0
0
0
1
1
1
0
0
0
1
1
0
1
1
1
0
0
0
0
0
0
1
0
0
0
1
1
0
"11101"
"11010"
"11011"
"11100"
"11110"
"11111"
"10110"
"10111"
"11000"
"11001"
1
0
0
1
0
PK22 (5
0)
PK23 (5
0)
PK24 (5
0)
PK25 (5
0)
PK26 (5
0)
PK27 (5
0)
PK28(5
0)
PK29 (5
0)
PK30 (5
0)
PK31 (5
0)