DocID018909 Rev 11
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RM0090
LCD-TFT Controller (LTDC)
511
Color Look-Up Table (CLUT)
The CLUT can be enabled at run-time for every layer through the
LTDC_LxCR
register and
it is only useful in case of indexed color when using the L8, AL44 and AL88 input pixel
format.
First, the CLUT has to be loaded with the R, G and B values that will replace the original R,
G, B values of that pixel (indexed color). Each color (RGB value) has its own address which
is the position within the CLUT.
The R, G and B values and their own respective address are programmed through the
LTDC_LxCLUTWR
register.
•
In case of L8 and AL88 input pixel format, the CLUT has to be loaded by 256 colors. The
address of each color is configured in the CLUTADD bits in the
LTDC_LxCLUTWR
register.
•
In case of AL44 input pixel format, the CLUT has to be only loaded by 16 colors. The
address of each color must be filled by replicating the 4-bit L channel to 8-bit as follows:
– L0 (indexed color 0), at address 0x00
– L1, at address 0x11
– L2, at address 0x22
– .....
– L15, at address 0xFF
@+7
A
x+3
[3:0]R
x+3
[3:0]
@+6
G
x+3
[3:0] B
x+3
[3:0]
@+5
A
x+2
[3:0]R
x+2
[3:0]
@+4
G
x+2
[3:0] B
x+2
[3:0]
L8
@+3
L
x+3
[7:0]
@+2
L
x+2
[7:0]
@+1
L
x+1
[7:0]
@
L
x
[7:0]
@+7
L
x+7
[7:0]
@+6
L
x+6
[7:0]
@+5
L
x+5
[7:0]
@+4
L
x+4
[7:0]
AL44
@+3
A
x+3
[3:0] L
x+3
[3:0]
@+2
A
x+2
[3:0] L
x+2
[3:0]
@+1
A
x+1
[3:0] L
x+1
[3:0]
@
A
x
[3:0] L
x
[3:0]
@+7
A
x+7
[3:0] L
x+7
[3:0]
@+6
A
x+6
[3:0] L
x+6
[3:0]
@+5
A
x+5
[3:0] L
x+5
[3:0]
@+4
A
x+4
[3:0] L
x+4
[3:0]
AL88
@+3
A
x+1
[7:0]
@+2
L
x+1
[7:0]
@+1
A
x
[7:0]
@
L
x
[7:0]
@+7
A
x+3
[7:0]
@+6
L
x+3
[7:0]
@+5
A
x+2
[7:0]
@+4
L
x+2
[7:0]
Table 89. Pixel Data mapping versus Color Format (continued)
ARGB8888