Palette
32 bytes
Palette
512 bytes
x bytes
Pixel Data
x bytes
Pixel Data
1, 2, 4, 12, 16, 24 BPP Modes
8 BPP Mode
Functional Description
13.3.5.2 Frame Buffer
A frame buffer is a contiguous memory block, storing enough data to fill a full LCD screen. For this device,
external memory needs to be used for the frame buffer. For specific details on which external memory
interface (EMIF) controller can be accessed by the LCD controller, see your device-specific data manual.
The data in the frame buffer consists of pixel values as well as a look-up palette.
shows the
frame buffer structure.
Figure 13-5. Frame Buffer Structure
NOTE:
•
8-BPP mode uses the first 512 bytes in the frame buffer as the palette while the other
modes use 32 bytes.
•
12-, 16-, and 24-BPP modes do not need a palette; i.e., the pixel data is the desired
RGB value. However, the first 32 bytes are still considered a palette. The first entry
should be 4000h (bit 14 is 1) while the remaining entries must be filled with 0. (For
details, see
.)
•
Each entry in a palette occupies 2 bytes. As a result, 8-BPP mode palette has 256 color
entries while the other palettes have up to 16 color entries.
•
4-BPP mode uses up the all the 16 entries in a palette.
•
1-BPP mode uses the first 2 entries in a palette while 2-BPP mode uses the first 4
entries. The remaining entries are not used and must be filled with 0.
•
In 12- and 16-BPP modes, pixel data is RGB data. For all the other modes, pixel data is
actually an index of the palette entry.
Table 13-8. Bits-Per-Pixel Encoding for Palette Entry 0 Buffer
Bit
Name
Value
Description
(1) (2) (3)
14-12
BPP
Bits-per-pixel.
000
1 BPP
001
2 BPP
010
4 BPP
011
8 BPP
1xx
12 BPP in passive mode (TFT_STN = 0 and STN_565 = 0 in RASTER_CTRL)
16 BPP in passive mode (TFT_STN = 0 and STN_565 = 1 in RASTER_CTRL)
16 BPP in active mode (LCDTFT = 1 and TFT24 = 0 in RASTER_CTRL)
24 BPP in active mode (LCDTFT = 1 and TFT24 = 1 in RASTER_CTRL)
(1)
Eight 1-bit pixels, four 2-bit pixels, and two 4-bit pixels are packed into each byte, and 12-bit pixels are right justified on (16-bit)
word boundaries (in the same format as palette entry).
(2)
For STN565, see the 16 BPP STN mode bit (
(3)
For Raw Data (12/16/24 bpp) framebuffers, no Palette lookup is employed therefore PALMODE = 0x10 in RASTER_CTRL.
1110LCD Controller
SPRUH73H – October 2011 – Revised April 2013
Copyright © 2011–2013, Texas Instruments Incorporated