Product specifications

VT8601A Apollo PLE133
Revision 1.82 October 22, 2001 -130 3D Graphics Engine Registers
Technologies, Inc.
Delivering Value
Delivering ValueDelivering Value
Delivering Value
GEbase + 7C – Alpha.........................................................RW
31-16 Reserved .........................................always reads 0
15-8 Source Constant Alpha
7-0 Destination Constant Alpha
GEbase + 84 – Bit Mask.....................................................RW
31-0 Bit Mask
One bits indicate that the corresponding color bit will
not be written to the frame buffer.
GEbase + 80 – Alpha Function .........................................RW
31-24 Reserved ......................................... always reads 0
23 Alpha Write
0 Disable ....................................................default
1 Enable. Draw each pixel with a blended alpha
value if alpha blending is enabled. Otherwise
draw with source alpha (the upper byte of the
Foreground Color register if not available).
This bit should be set in 8-bit and 16-bit color modes.
22 Constant Source Alpha
0 Disable ...................................................default
1 Enable
21 Constant Destination Alpha
0 Disable ...................................................default
1 Enable
20 Result Alpha
0 The result of blending ............................default
1 Source alpha
19-16 Alpha Test Function
0000 Never accept the pixel
0001 Accept if alpha < reference alpha
0010 Accept if alpha == reference alpha
0011 Accept if alpha <= reference alpha
0100 Accept if alpha > reference alpha
0101 Accept if alpha != reference alpha
0110 Accept if alpha >= reference alpha
0111 Always accept the pixel
1xxx -reserved-
15-8 Reference Alpha Value
7-4 Destination Blending Factor
0000 (0,0,0,0)
0001 (1,1,1,1)
0010 (RS,GS,BS,AS)
0011 (1,1,1,1) - (RS,GS,BS,AS)
0100 (AS,AS,AS,AS)
0101 (1,1,1,1) – (AS,AS,AS,AS)
0110 (AD,AD,AD,AD)
0111 (1,1,1,1) – (AD,AD,AD,AD)
1xxx -reserved-
3-0 Source Blending Factor
0000 (0,0,0,0)
0001 (1,1,1,1)
001x -reserved-
0100 (AS,AS,AS,AS)
0101 (1,1,1,1) – (AS,AS,AS,AS)
0110 (AD,AD,AD,AD)
0111 (1,1,1,1) – (AD,AD,AD,AD)
1000 (RD,GD,BD,AD)
1001 (1,1,1,1) - (RD,GD,BD,AD)
1010 (F,F,F,1); F = min (AS, 1-AD)
1011 -reserved-
11xx -reserved-