Product specifications

VT8601A Apollo PLE133
Revision 1.82 October 22, 2001 -126 3D Graphics Engine Registers
Technologies, Inc.
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GEbase + 44 – Drawing Command ..................................RW
Writing to the Drawing Command register starts a drawing
operation. When this register is set, the drawing environment
registers and memory interface registers are locked in. Any
change to these registers will not affect this drawing operation.
Furthermore, the Pixel Engine will not accept any data from
the host or from the Rasterization Engine without a drawing
command. After a drawing command is issued, the Pixel
Engine will selectively accept data from the host or
Rasterization Engine depending on the command.
Specifically, the Pixel Engine only accepts data from the host
if the command is text or blt and the BS field indicates the
source is from the host. The Pixel Engine only accepts data
(scanlines, Z, color, etc.) from the Rasterization Engine if the
command is line or polygon.
31-28 Operation Code
0000 Null Command....................................... default
0001 -reserved-
0010 Line
0011 -reserved-
01xx -reserved-
1000 Bit-Blt (see note below)
1001 Text (see note below)
1010 (See BitBlt)
1011 Trapezoid / Polygon
1100 (See Bit Blt)
1101 (See Text)
1110 Trapezoid / Polygon
1111 -reserved-
Note: for Text and BitBlt opcodes, bit 29 indicates
whether the PE can accept data from the host
while bit-30 indicates whether the PE can
accept data from the RE.
27 Line Style
0 No style, solid line, or other operation (blt,
polygon, text)
1 Style line
26 Z Operations
0 Disable Z operations (must be 0 for text, blt)
1 Enable Z operations
25 Alpha Test
0 Disable (must be 0 for text)
1 Enable
24 Texture Function
0 Disable (must be 0 for blt, text)
1 Enable
23 Alpha Blending
0 Disable (must be 0 for text)
1 Enable
22 Specular Color
0 Disable (must be 0 for blt, text)
1 Enable
21 Fog
0 Disable (must be 0 for blt, text)
1 Enable
20 Source Color Expansion
0 Disable
1 Enable (bits 26-21 must be 0)
19 Source Color
0 Transparent (applies to mono source and
constant color line)
1 Opaque (should be enabled for any operation
with a “solid Source”, such as Gouraud
shading, constant color fill, color to screen blt,
texture mapping, etc.)
18-17 Source Surface ID
16-15 Destination Surface ID
14-12 Source Offset
Mono source pixel offset. Bit-19 must be 1.
11 Double Specular Color
0 Disable
1 Enable. Specular color (RGB) is doubled
before being added to diffuse color.
10 Texture Transparency
0 Disable texture color key
1 Enable texture color key
9 Lit-Texture
0 Disable
1 Enable
8 Dither
0 Disable
1 Enable. Use 4x4 dither matrix (including fog
and alpha)
7 Source Color Key
0 Disable
1 Enable (Key is FG)
6 Destination Color Key
0 Disable
1 Enable
5 Bit Mask
0 Disable
1 Enable
4 ROP
0 Disable
1 Enable
3-2 Blt Source or Constant Color Line or Polygon
00 Source from host (bits 26-20 must be 0 for blt)
01 Source from frame buffer
10 Source is constant (FG). Includes constand
line and constant polygon.
11 Block write fill
This field must be set to 00 for text / line / polygon.
1 Blt Direction (BLT Only)
0 Positive direction in X and Y
1 Negative direction in X and Y
Must be set to 0 for polygons, lines, and text.
0 Clipping
0 Disable
1 Enable