GD32F20x User Manual
598
23.5.3.
Pixel formats
The Pixel DMA pushes pixel data into PPU in word format and PPU (Pixel Process Unit) is
responsible for converting various pixel formats into an internal ARGB8888 format. TLI
supports up to eight pixel formats as shown in the table below. The PPF[2:0] in TLI_LxPPF
register defines the pixel format.
ARGB8888 format needs 8-bits data in each channel (Alpha, Red, Green and Blue), while
ARGB1555 and ARGB4444 formats have fewer bits than 8 in some channels. PPU converts
these formats into ARGB8888 by filling LSBs with MSBs for each channel. When processing
RGB888 and RGB565 formats, PPU assumes that Alpha=255 and also fill filling LSBs with
MSBs if the channel bit number less than 8.
AL88, AL44 and L8 formats are LUT (Look-Up-Table) formats. In these channels, L is the
address of the look-up table. TLI has 2 internal look-up tables: one for each layer. The internal
look-up table size is 256x24 bits (256 entries and each entry stores a 24-bits RGB value).
When processing LUT format pixel, PPU reads out an entry from the look-up table and uses
this entry as the RGB value. Because the address of look-up table is 8-bit, PPU also fill LSBs
with MSBs if L channel has bits less than 8. The entries in the look-up tables are uninitialized
after reset, so the application should initialize the look-up table with proper value using
TLI_LxLUT register before display a look-up table format layer. The TLI_LxLUT is a write-only
register and a write operation to this register will write an entry to the look-up table.
Each layer is able to be configured into color keying mode. The register TLI_LxCKEY defines
a RGB value. When color keying mode is enabled for a layer, PPU will compare each RGB
value of each pixel in this layer with the TLI_LxCKEY and force the pixel
’s ARGB value to 0
if the value matches.
Table 23-2. Supported pixel formats
PPF[2:0]
Pixel Format
000
ARGB8888
001
RGB888
010
RGB565
011
ARGB1555
100
ARGB4444
111
AL88
101
L8
110
AL44
23.5.4.
Layer window and blending function
TLI supports window function for each layer and blending function between two layers. TLI
first perform window operation to each layer and then blend two layers into a frame.
The window function defines a display window, and each layer has separate window
parameters defined by TLI_LxHPOS and TLI_LxVPOS registers. These window parameters
Summary of Contents for GD32F20 Series
Page 191: ...GD32F20x User Manual 191 Bits Fields Descriptions 31 0 TRNDATA 31 0 32 Bit Random data ...
Page 290: ...GD32F20x User Manual 290 conversion is ongoing ...
Page 325: ...GD32F20x User Manual 325 15 0 ALRM 15 0 RTC alarm value low ...
Page 385: ...GD32F20x User Manual 385 ...
Page 523: ...GD32F20x User Manual 523 clears AERR bit by writing 0 to it ...