MB86290A Datasheet, PDF (71/184 Pages) Fujitsu Component Limited. – Graphics Controller Hardware Specifications

6.5.2 Alpha Blending
Alpha blending blends the pixel’s native color and current color of that pixel
position according to the blending ratio parameter set in the alpha register.
This function cannot be used simultaneously with logical calculation. It can
be used only when the direct color mode (16 bits/pixel) is used. The blended
color C is calculated as shown below when the native color of the pixel to be
rendered is CP, the current pixel color of that position is CF, and the alpha
value set in the alpha register is A:
C = CP × A + (1-A) × CF
The alpha value is specified as 8-bit data. 00h means alpha value 0% and
FFh means alpha value 100%. When the texture mapping function is
enabled, the following blending modes are applicable:
Normal
Blends post texture mapping color with current frame buffer color
St e nc i l
Uses MSB of texcel color to select display color:
MSB = 1: Texcel color
MSB = 0: Current frame buffer color
Stencil alpha
Uses MSB of texcel color to select and activate alpha-blend function:
MSB = 1: Alpha blend texcel color and current frame buffer color
MSB = 0: Current frame buffer color
6.5.3 Logical Calculation
This mode executes a logical calculation between the new pixel color to be
rendered and the current frame memory color and displays the result. Alpha
blending cannot be used when this function is used.
Type
CLEAR
COPY
NOP
SET
COPY INVERTED
INVERT
AND REVERSE
OR REVERSE
ID
0000
0011
0101
1111
1100
1010
0010
1011
Operation
0
S
D
1
!S
!D
S & !D
S | !D
Type
AND
OR
NAND
NOR
XOR
EQUIV
AND INVERTED
OR INVERTED
ID
0001
0111
1110
1000
0110
1001
0100
1101
Operation
S&D
S|D
!(S & D)
!(S | D)
S xor D
!(S xor D)
!S & D
!S | D
71