20.3.6.2.1 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, and 24 bpp, an 8-word palette buffer is read from DDR by the DMA. If the bpp field in the first entry is 8 bpp, a 128-word palette is 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, and 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, and 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 20-4.