at91sam9263 ATMEL Corporation, at91sam9263 Datasheet - Page 872

• Manufacturer Part Number: at91sam9263
• Description: At91 Arm Thumb Microcontrollers
• Manufacturer: ATMEL Corporation

Table 43-7.
43.5.2.6
872
Address
00
01
...
FE
FF
AT91SAM9263 Preliminary
Intensity_bit_0
Intensity_bit_1
Intensity_bit_254
Intensity_bit_255
Dithering
Lookup Table Structure in the Memory
map. The LUT is mapped as 16-bit half-words aligned at word boundaries, only word write
access is allowed (the 16 MSB of the bus are not used). For the detailed memory map, see
Table 43-13 on page
The lookup table contains 256 16-bit wide entries. The 256 entries are chosen by the program-
mer from the 2
For the structure of each LUT entry, see
In STN Monochrome, only the four most significant bits of the red value are used (16 gray
shades). In STN Color, only the four most significant bits of the blue, green and red value are
used (4096 colors).
In TFT mode, all the bits in the blue, green and red values are used (32768 colors). In this mode,
there is also a common intensity bit that can be used to double the possible colors. This bit is the
least significant bit of each color component in the LCDD interface (LCDD[18], LCDD[10],
LCDD[2]). The LCDD unused bits are tied to 0 when TFT palletized configurations are used
(LCDD[17:16], LCDD[9:8], LCDD[1:0]).
The dithering block is used to generate the shades of gray or color when the LCD Controller is
used with an STN LCD Module. It uses a time-based dithering algorithm and Frame Rate Con-
trol method.
The Frame Rate Control varies the duty cycle for which a given pixel is turned on, giving the dis-
play an appearance of multiple shades. In order to reduce the flicker noise caused by turning on
and off adjacent pixels at the same time, a time-based dithering algorithm is used to vary the
pattern of adjacent pixels every frame. This algorithm is expressed in terms of Dithering Pattern
registers (DP_i) and considers not only the pixel gray level number, but also its horizontal
coordinate.
Table 43-8
Table 43-8.
Gray Level
15
14
13
12
11
10
shows the correspondences between the gray levels and the duty cycle.
Blue_value_0[4:0]
Blue_value_1[4:0]
Blue_value_254[4:0]
Blue_value_255[4:0]
16
Dithering Duty Cycle
possible combinations.
891.
Duty Cycle
1
6/7
4/5
3/4
5/7
2/3
Data Output [15:0]
Table
Green_value_0[4:0]
Green_value_1[4:0]
Green_value_254[4:0]
Green_value_255[4:0]
43-7.
Pattern Register
-
DP6_7
DP4_5
DP3_4
DP5_7
DP2_3
Red_value_0[4:0]
Red_value_1[4:0]
Red_value_254[4:0]
Red_value_255[4:0]
6249D–ATARM–20-Dec-07