MB87P2020 Datasheet, PDF (112/356 Pages) Fujitsu Component Limited. – Colour LCD/CRT/TV Controller

MB87J2120, MB87P2020-A Hardware Manual
mode guarantees a direct connection between PP an SDC without pixel data and pixel address manipulation
by AAF (AAU is off).
The control block realizes reading or writing of configuration registers. The anti aliasing unit manipulates
the pixel data and manages the access to PP and SDC.
1.1.2 AAU Function
The main function of the anti aliasing algorithm is to reduce the staircasing effect. This effect is a result of
projecting (drawing) objects onto the physical pixel resolution of the display. To get a higher image quality
the implemented super sampling algorithm could be used to avoid stair effects on the edges of objects, e.g.
lines or circles. In this case the anti aliasing is done on the fly, that means that during the drawing of objects
the object itself is antialiased with the current background. This results in smoother edges by averaging fore-
ground and background color information.
1.1.2.1 Super Sampling
The objects are drawn at a higher resolution, which per definition leads to less staircasing. This virtual res-
olution is doubled in X and Y direction for 2x2 super sampling or four times in both dimensions for 4x4
super sampling. The image is then converted to the normal resolution by averageing the sub pixels to a new
resulting pixel, which is stored in video RAM. Foreground pixels are generated by PixelProcessor or written
through its interface. Background pixels are read from memory.
Figure 1-2: Antialiasing with super sampling. From left to right: Without antialiasing, doubled resolu-
tion with sub-pixels, averaging of sub-pixels.
1.1.2.2 Drawing Resolution
The super sampling method requires doubled or four times the drawing resolution. If antialiasing is enabled,
coordinates have to be doubled or multiplied by four. The Pixel Processor did not enhance the resolution
automatically. It is the task of the application to work on the finer resolution of the sub-pixel grid.
A side-effect of the high er resolution is that the amount of generated pixel data is four or sixteen times high-
er compared to the original picture without antialiasing. Additional each write access converts to a read-
modify-write access du to the fact that background information is required. This has to be considered in
terms of drawing performance. To reduce the effect of the high number of read-modify-write (RMW) ac-
cesses to the same pixel coordinate write-back optimization is implemented for subsequent writes to the
same pixel address. It is recommended to switch on optimization by setting OPTI_EN to ’1’.
1.1.2.3 Data and Address Processing
The algorithm is based on single pixel processing due to sequential averaging in video memory. Therefore
PP is forced to block mode, each pixel data requires its own address information. Packet data formats are
not supported (e.g. PutPxWd). Incoming PP requests of variable block size were divided into single RMW
accesses to the SDC. Thats why some restrictions apply during AAF usage, which will be discussed in sec-
tion 1.3.1.
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