SLAU723A October 2017 – October 2018 MSP432E401Y , MSP432E411Y
When palette RAM is enabled for 1-, 2-, and 4-bpp frame storage, the palette buffer is 16 word entries, where the upper half of the word is unused. The first entry of the palette RAM contains the encoding for the palette type (1, 2, 3, 6, or 12, 16, 24) of the stored picture on bits [14:12], as well as the first input code for one palette entry (bits [11:0]). Subsequent entries only contain the input codes for next palette entries. Figure 20-4 shows the frame buffer structure.
For 1-bpp source pictures, the first two palette entries are valid; for 2-bpp sources, the first four palette entry sources are valid; for 4-bpp, all 16 palette entries are valid. Even if the palette entries are not valid for a particular type, there is a fixed number of 8 words reserved for the palette RAM.
The first palette entry represents the RGB value for the source pixel encoded as 0x0. The second palette entry represents the RGB value for the source pixel encoded as 0x1, and so on, such that the sixteenth palette entry is used to represent the RGB value for a pixel encoded as 0xF.
Source data encoded as 12, 16, or 24 bpp do not use the palette RAM since the encoded data already represents the actual RGB values. However, 16 palette RAM entries still precede the picture data in this case and the first palette entry must still define the bpp in bits [14:12]. The type field encoding is defined below in Table 20-3
First Palette RAM Entry [14:12] | Source Image Type |
---|---|
0x0 | 1 bpp |
0x1 | 2 bpp |
0x2 | 4 bpp |
0x3 | 8 bpp |
0x4 | 12, 16, or 24 bpp |