STM7710

Architecture

17/23

2.13

2D blitter

The 2D-graphics processor (also called the blitter engine) is a CPU-independent engine for

graphics picture processing. It functions as a dual-source 2D DMA, with a set of powerful

operators.

The 2D-graphics processor receives data from local memory through two input sources:

source 1 and source 2. Source 1 is used for frequent operations such as color-fill or simple

source-copy; it has a 64-bit wide internal bus and performs according to the pixel format. All

operators always apply to source 2. The processing pipeline bus is always a pixel bus

(ARGB8888 format) whatever the format of the source inputs. Sources 1 and 2 are used

simultaneously for read/modify/write operations.

The 2D-graphics processor is software controlled by a link-list mechanism. Each node of the

link list is an instruction that contains all the necessary information to proceed.

The STM7710 blitter features:

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solid color fill of rectangular windows,

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solid color shade (fill + alpha blending),

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one source copy, with one or several operators enabled (color format conversion, 2D

scaling),

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two-source copy with alpha blending or logical operation between them,

●

4:2:2 raster/macroblock and 4:2:0 macroblock as source formats, 4:2:2 raster as a

destination format,

●

color space conversion RGB to and from YCbCr.

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color expansion (CLUT to true color),

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color correction (gamma, contrast, gain),

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color reduction (true color to ACLUTn) using an error diffusion algorithm,

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2D resize engine with high-quality filtering,

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adaptive flicker filter from memory to memory,

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color keying capability,

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rectangular clipping,

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programmable source/target scanning direction, both horizontally and vertically, to

cope correctly with overlapping source and destination areas,

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1-bit/8-bit clipmask bitmap for random shape clipping can be achieved in two passes.

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plane mask feature available,

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special XYLC access mode, for speeding random pixel access, or horizontal line

drawing (polygon filling, run-length decoder accelerator).

Source and destination windows can all be defined using an XY descriptor, with pixel

accuracy whatever the format, from 1 to 32 bpp. Most of these operators can be combined

in a single blitter pass: for example, convert a YCbCr 4:2:2 bitmap to 4:4:4 RGB, resize it

and blend it on an RGB565 background picture.