ST STM32F405 Reference Manual page 508

LCD-TFT controller (LTDC)
16.7.21 LTDC Layerx Blending Factors Configuration Register (LTDC_LxBFCR)
(where x=1..2)
This register defines the blending factors F1 and F2.
The general blending formula is: BC = BF1 x C + BF2 x Cs
•
BC = Blended color
• BF1 = Blend Factor 1
•
C = Current layer color
•
BF2 = Blend Factor 2
•
Cs = subjacent layers blended color
Address offset: 0xA0 + 0x80 x (Layerx -1), Layerx = 1 or 2
Reset value: 0x0000 0607
31 30 29 28
15 14 13 12
Reserved
Bits 31:11 Reserved, must be kept at reset value
Bits 10:8 BF1[2:0]: Blending Factor 1
Bits 7:3 Reserved, must be kept at reset value
Bits 2:0 BF2[2:0]: Blending Factor 2
508/1749
27 26 25
11 10 9
BF1[2:0]
rw rw
These bits select the blending factor F1
000: Reserved
001: Reserved
010: Reserved
011: Reserved
100: Constant Alpha
101: Reserved
110: Pixel Alpha x Constant Alpha
111:Reserved
These bits select the blending factor F2
000: Reserved
001: Reserved
010: Reserved
011: Reserved
100: Reserved
101: 1 - Constant Alpha
110: Reserved
111: 1 - (Pixel Alpha x Constant Alpha)
RM0090 Rev 18
24 23 22 21
Reserved
8 7 6 5
Reserved
rw
20 19 18 17
4 3 2 1
BF2[2:0]
rw rw
RM0090
16
0
rw