VT8601 Via, VT8601 Datasheet - Page 124

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

GEbase + 3C –Setup Engine Primitive Type ................. WO
Writing to this register signals the Graphics Engine to begin
sequential loading. The engine will interpret the contents of
this register and the Primitive Attribute register to decide the
amount and types of parameters to expect. Like vertices, there
is a FIFO for Triangle Attributes. The queue has three entries.
Writing to this register adds it to the queue. The Setup Engine
starts working whenever a triangle attribute is received and
stops after it is finished processing a triangle with L = 1.
Revision 1.3 September 8, 1999
31-30 Loading Target
27-26 Culling Attribute (Setup Engine Target Only)
20-19 Working Vertex Index
18-3 Reserved
1-0
29
28
25
24
23
22
21
2
7HFKQRORJLHV ,QF
Null Primitive
Last Primitive
Reserved
(V2, V0) Edge Anti-Aliasing Flag ........... default = 0
(V1, V2) Edge Anti-Aliasing Flag .......... default = 0
(V1, V1) Edge Anti-Aliasing Flag .......... default = 0
Full Vertices Information
Index of the working vertex that is to be replaced.
This field is always 0 if F = 1.
Debug Control
Flat Color Vertex Index
Vertex index for flat color (Index of vertex whose
color is passed to the RE as the starting color)
:H &
:H &R R QQHFW
00 Rasterization Engine. Send bits 19-0 to the
01 Setup Engine.
1x -reserved-
00 No culling...............................................default
01 Clockwise culling
10 Counter-clockwise culling
11 No culling
0
1
0
1
0
1
0
1
QQHFW
RE. Sequential loading data will also be sent
to the RE.................................................default
Sequential loading data will also be sent to the
SE. Internally, a flag is set to prevent the SE
from decoding the data and sending it to the
RE. The SE will clear this flag when it is idle.
Regular Primitive ...................................default
Null Primitive
Regular Primitive ...................................default
Last Primitive
Partial Vertices Information.
vertices are from the previous triangle. Only
one vertex is to be loaded from the vertex
queue to the working registers................default
All vertices are new.
registers are to be loaded from the vertex
queue.
Discard triangle on overflow..................default
Draw triangle on overflow
........................................ always reads 0
........................................ always reads 0
Send bits 29-0 to the SE.
All three working
Two of the
-118
Vertex Registers
Inside the setup engine, one set of registers is provided to
store the three vertices is is currently working on and an
additional set is provided to store three pending vertices. Note
that it doesn’t always require 3 vertices to define a triangle
(depending on the Triangle Attribute Register, it may be either
1 or 3 vertices).
Vertex information includes coordinate, texture, color, and
depth. Some may be absent in a data stream. If any appear in
a vertex, they must be present in the following order: Color,
Specular Color, W, U, V, Z, X, Y. The formats are shown
below:
Vertex Register 1 - Color Value
Vertex Register 2 - Specular Color Value
Vertex Register 3 - W Value
Vertex Register 4 - U Value
Vertex Register 5 - V Value
Vertex Register 6 - Z Value
Vertex Register 7 - X Value
Vertex Register 8 - Y Value
Floating Point Number Format
All floating point numbers are converted by on-chip hardware
into internal fixed point integer format. All floating point
numbers are specified in IEEE 32-bit floating point number
format (shown below):
31-24 Alpha Value
23-16 Red Value
31-24 Fog Value
23-16 Specular Red Value
30-23 Exponent (excess-127 format)
15-8 Green Value
15-8 Specular Green Value
31-0 Texture W Coordinate. 32-bit floating # in (0, 1.0)
31-0 Texture U Coordinate. 32-bit floating number
31-0 Texture V Coordinate. 32-bit floating number
31-0 Z Coordinate. 32-bit floating number
31-0 X Coordinate. 32-bit floating number
31-0 Y Coordinate. 32-bit floating number
22-0 Mantissa (fractional part of a number in “1.nn”
7-0
7-0
31
Blue Value
Specular Blue Value
Sign
format where the integer part is always 1)
VT8601 Apollo ProMedia
3D Graphics Engine Registers