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Graphics Register Reference
TVP4020
Programmers Reference Manual
222
Name:
Logic Op Mode
Unit:
Logic Op
Region: 0
Offset:
0x0000.8828
Tag:
0x0105
Reset Value:
Undefined
Read/write
0
8
16
24
31
Reserved
LogicalOp enable
UseConstantFBWriteData
LogicOp
Controls Logical Operations on the framebuffer.
The UseConstantFBWriteData bit when set to one, causes the color value in the
FBWriteData register to be written to the framebuffer, rather than the fragment's color. This
can achieve higher bandwidth into the framebuffer for flat shaded primitives, but may only
be used when LogicalOps are disabled (bit 0 cleared to 0)
Bit0
Logic Op Enable:
0 = Disable
1 = Enable
Bit1-4
Logic Op:
Mode
Name
Operation
Mode
Name
Operation
0
CLEAR
0
8
NOR
~(S | D)
1
AND
S & D
9
EQUIV
~(S ^ D)
2
AND REVERSE
S & ~D
10
INVERT
~D
3
COPY
S
11
OR REVERSE
S | ~D
4
AND INVERTED
~S & D
12
COPY INVERT
~S
5
NO-OP
D
13
OR INVERT
~S | D
6
XOR
S ^ D
14
NAND
~(S & D)
7
OR
S | D
15
SET
1
Where:
S = Source (fragment) color, D = Destination (framebuffer) color.
Bit5
UseConstantFBWriteData:
0 = Variable
1 = Constant
LogicalOpMode
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 ...