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MB86R02 'Jade-D' Hardware Manual V1.64
20 Dither Unit
20.1 Overview
A dither unit is required in a display processing pipe line to display images on a graphic device which
has less color levels than those contained in the original picture data in order to obtain a better visual
result. To achieve this, the dither unit modifies pixels in such a way that the average color level of
these pixels is used.
HSYNC_I, VSYNC_I
VALID_I
RGB_I
STOP_O
20.1.1 Features
The dither unit supports:
• Bypass mode
In bypass mode, the input data will be passed to the output, where the 2 LSB of the input data will
be dropped.
• Spatial dithering mode
In spatial dithering mode, the intensities of neighboring pixels are modified so that their combined
intensities average out to the desired value. Using a 4x4 matrix (see table 1.1.1), the incoming pixel
value will be filtered depending on the location of the pixel in a frame. The pixel location is
generated according to the horizontal and vertical synchronization signals.
0
8
2
10
12
4
14
6
3
11
1
9
15
7
13
5
Table 1.1.1 : 4x4 Ordered dither matrix
Config
DITH
Figure 20-1 DITH inputs/outputs
HSYNC_O, VSYNC_O
VALID_O
RGB_O
STOP_I
20-1
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