Datasheet

Table 26-6. Type Encoding in Palette Entry 0 Buffer
Source Image TypeFirst Palette RAM Entry [14:12]
1 bpp0x0
2 bpp0x1
4 bpp0x2
8 bpp0x3
12, 16, or 24 bpp0x4
26.3.5.2 Palette RAM Structure for 8 Bits Per Pixel
For image sources that are 8 bpp, 256 palette entries (2
8
) are required. This structure of the palette
RAM is similar to the one described for 1, 2, 4, or 4 bpp except that the palette requires 256 entries
(128 words), instead of 16. The first palette entry again contains the "type" definition of the picture
along with the RGB values in bits [11:0].
26.3.5.3 LCD RAM Configuration
The LCD RAM can be configured to hold palette only, picture data only or both palette and picture
data. Depending on the mode, the RAM is used differently:
■ Palette Only: The PALMODE field in the LCD Raster Control (LCDRASTRCTL) register is
programmed to 0x01. If the type field in the first palette entry is for 1, 2, 4, or 12/16/24 bpp, an
8 word palette buffer will be read from DDR by the DMA. If the bpp field in the first entry is 8 bpp,
a 128 word palette will be loaded by the DMA. Note that the DMA Frame Buffer n Base Address
(LCDDMABAn) and LCD DMA Frame Buffer n Ceiling Address (LCDMACAn) registers must
encompass the palette information size. Note that although an 8 word buffer is created for
12/16/24 bpp, it is ignored during data transfers.
■ Data Only: When PALMODE is programmed to 0x10, the bpp field from the last palette read is
used. Thus, a single palette in DDR can be associated with multiple stored pictures in DDR,
enabling the palette loading to occur once (PALMODE = 0x01) and subsequent data-only frame
buffers to be transferred by the DMA into the RAM (PALMODE = 0x10). For 12/16/24 bpp frames
the bpp field in the previously read palette RAM buffer is irrelevant.
■ Palette and Data: When the PALMODE encoding is 0x00, the frame buffer is comprised of palette
data followed immediately by pixel information. For 12, 14, and 24 bit (packed or unpacked) raw
formats, an 8 word palette is prepended to the pixel data. Thus, palette information will be read
from DDR even though it is not applicable data and the configuration will look similar to Figure
26-4 on page 1858.
26.3.5.4 Raw Data and Color Component Formats
Depending on the value programmed in the raster control register you can have different color
formats. Raw data formats are used for active matrix panels. The LCD controller supports, 24 bpp,
16 bpp and 12 bpp raw formats.
Note: The TYPE code in the first palette entry must be set to "1XX" for 12/16/24 bpp raw data
formats.
Data Format for 24 bpp
For raw formats used in active matrix panels, the palette RAM provides a 12 bpp output, or a color
depth of 12 bits (4096 colors per pixel). Data formats of 24 bpp can be stored in packed or unpacked
1859December 13, 2013
Texas Instruments-Advance Information
Tiva
™
TM4C129XNCZAD Microcontroller