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266 AMD Geode™ LX Processors Data Book
Graphics Processor Register Definitions
33234H
GP_RASTER_MODE Bit Descriptions
Bit Name Description
31:28 BPP/FMT Color Depth and Format.
0000: 8-bpp, 3:3:2 format.
0100: 16-bpp, 4:4:4:4 format.
0101: 16-bpp, 1:5:5:5 format.
0110: 16-bpp, 0:5:6:5 format.
1000: 32-bpp, 8:8:8:8 format.
All Others: Undefined.
27:24 RSVD Reserved. Write as read.
23:22 EN Alpha Enable Bits. Also used to select how to apply the specified operation.
00: Alpha disabled/ROP enabled.
01: Alpha operation applies to only the RGB values of the pixel. Output alpha is from
channel B if the OS is 01; otherwise from channel A.
10: Alpha operation applies to only the alpha of the pixel. Output RGB is from channel B
if the OS is 01; otherwise from channel A.
11: Alpha operation applies to all channels of the pixel (ARGB).
21:20 OS Alpha Operation Select. Determines the alpha operation to be performed if enabled.
00: a∗A.
01: (1-a)*B.
10: A + (1-a)*B.
11: a∗A + (1-a)*B.
* Channel A is added in this case only if the selected α is also from channel A.
19:17 AS Alpha Select. Chooses which alpha value to use for the multiplication.
000: a
A
100: Color
A
001: a
B
101: Color
B
010: a
R
110: a
R
011: Constant 1 111: Constant 1
16 CS Channel Select. Determines which data stream gets put on which channel.
0: A is source, B is destination.
1: A is destination, B is source.
15:14 RSVD Reserved. Write as read.
13 SI Source Invert. Inverts the sense of monochrome source data.
12 PI Pattern Invert. Inverts the sense of monochrome pattern data.
11 ST Source Transparency. Enables transparency for monochrome source data and color
keying for color source data.
0: Disable.
1: Enable.
10 PT Pattern Transparency. Enables transparency for monochrome pattern data.
0: Disable.
1: Enable.
9:8 PM Pattern Mode. Specifies the format of the pattern data.
00: Solid pattern. Pattern data always sourced from GP_PAT_COLOR_0 (GP Memory
Offset 18h).
01: Mono pattern.
10: Color pattern.
11: Undefined.