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TVP4020
Programmers Reference Manual
Graphics Programming
121
5.14
Logical Op Unit
The Logical Op unit performs three functions:
•
logic operations between the fragment color (source color) and a
value from the framebuffer (destination color)
•
software writemasking
•
optional control of a special P
ERMEDIA
mode which allows flat shading
rendering.
5.14.1
Logical Operations
The logical operations supported by P
ERMEDIA
are:
Mode
Name
Operation
0
Clear
0
1
And
S & D
2
And Reverse
S & ~D
3
Copy
S
4
And Inverted
~S & D
5
No-op
D
6
Xor
S ^ D
7
Or
S | D
8
Nor
~(S | D)
9
Equivalent
~(S ^ D)
10
Invert
~D
11
Or Reverse
S | ~D
12
Copy Invert
~S
13
Or Invert
~S | D
14
Nand
~(S & D)
15
Set
1
Where:
S = Source (fragment) Color, D = Destination
(framebuffer) Color
Table 5.20
Logical Operations
For correct operation of this unit in a mode which takes the destination
color, P
ERMEDIA
must be configured to allow reads from the framebuffer
using the FBReadMode register. See section §5.10 for more details.
P
ERMEDIA
makes no distinction between RGBA and CI modes when
performing logical operations. However, logical operations are generally
only used in CI mode.
Summary of Contents for TVP4020 PERMEDIA 2
Page 1: ...Texas Instruments TVP4020 PERMEDIA 2 Programmer s Reference Manual Issue 4 ...
Page 284: ...TVP4020 Programmers Reference Manual A Gouraud Shaded Triangle 275 ...
Page 292: ...TVP4020 Programmers Reference Manual Register Tables 283 ...
Page 314: ...TVP4020 Programmers Reference Manual Index 305 ...
Page 315: ...Index TVP4020 Programmers Reference Manual 306 Index ...
Page 323: ...Index TVP4020 Programmers Reference Manual 314 ...