VT8601 Via, VT8601 Datasheet - Page 133

• Manufacturer Part Number: VT8601
• Description: Slot-1 / Socket-370 PCI North Bridge
• Manufacturer: Via

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
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.
Revision 1.3 September 8, 1999
31-28 Operation Code
27
26
25
24
23
22
21
7HFKQRORJLHV ,QF
Note: for Text and BitBlt opcodes, bit 29 indicates
Line Style
Z Operations
Alpha Test
Texture Function
Alpha Blending
Specular Color
Fog
:H &
:H &R R QQHFW
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-
0
1
0
1
0
1
0
1
0
1
0
1
0
1
QQHFW
whether the PE can accept data from the host
while bit-30 indicates whether the PE can
accept data from the RE.
No style, solid line, or other operation (blt,
polygon, text)
Style line
Disable Z operations (must be 0 for text, blt)
Enable Z operations
Disable (must be 0 for text)
Enable
Disable (must be 0 for blt, text)
Enable
Disable (must be 0 for text)
Enable
Disable (must be 0 for blt, text)
Enable
Disable (must be 0 for blt, text)
Enable
Engine
depending
on
the
command.
-127
18-17 Source Surface ID
16-15 Destination Surface ID
14-12 Source Offset
3-2
20
19
11
10
9
8
7
6
5
4
1
0
Source Color Expansion
Source Color
Mono source pixel offset. Bit-19 must be 1.
Double Specular Color
Texture Transparency
Lit-Texture
Dither
Source Color Key
Destination Color Key
Bit Mask
ROP
Blt Source or Constant Color Line or Polygon
This field must be set to 00 for text / line / polygon.
Blt Direction (BLT Only)
Must be set to 0 for polygons, lines, and text.
Clipping
00 Source from host (bits 26-20 must be 0 for blt)
01 Source from frame buffer
10 Source is constant (FG). Includes constand
11 Block write fill
0
1
0
1
0
1
0
1
0
1
0
1
0
1
0
1
0
1
0
1
0
1
0
1
Disable
Enable (bits 26-21 must be 0)
Transparent (applies to mono source and
constant color line)
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.)
Disable
Enable.
before being added to diffuse color.
Disable texture color key
Enable texture color key
Disable
Enable
Disable
Enable. Use 4x4 dither matrix (including fog
and alpha)
Disable
Enable (Key is FG)
Disable
Enable
Disable
Enable
Disable
Enable
line and constant polygon.
Positive direction in X and Y
Negative direction in X and Y
Disable
Enable
VT8601 Apollo ProMedia
Specular color (RGB) is doubled
3D Graphics Engine Registers