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Memory I/O and Organization
TVP4020
Programmers Reference Manual
26
localbuffer data cannot be greater than 16 bits. If a Stencil field is
defined then it occupies bit 15; the depth field always starts at bit 0.
The format of the localbuffer is specified in two places: the
LBReadFormat register and the LBWriteFormat register.
4.2.1
Localbuffer Coordinates
The translation from the internal coordinate system to the external
address map involves setting the base address of the window (or screen
if coordinates are screen relative) and positioning the origin in either the
top left or bottom left corner. The origin is specified in the LBReadMode
register.
The actual equations used to calculate the localbuffer address to read
and write are:
Bottom left origin
Destination address = LBWindowBase - Y * W + X
Source address = LBWindowBase - Y * W + X + LBSourceOffset
Top left origin
Destination address = LBWind Y * W + X
Source address = LBWind Y * W + X + LBSourceOffset
where:
X
is the pixel's X coordinate.
Y
is the pixel's Y coordinate.
LBWindowBase holds the base address in the localbuffer of the
current window.
LBSourceOffset is normally zero except during a copy operation
where data is read from one address and
written to another address. The offset between
source and destination is held in the
LBSourceOffset register.
W
is the screen width. Only a subset of widths are
supported and these are encoded into the PP0,
PP1 and PP2 fields in the LBReadModeregister.
See the table in Appendix C for more details.
This produces the localbuffer address in pixels. For P
ERMEDIA
, the
localbuffer data is always 16 bits so the physical byte address is two
times the pixel address. The destination address is the address that data
will be written to; data may also be read from this address if read-modify-
write operations are needed such as depth testing. The source address
is mainly used for copy operations and is only used for reading data.
Содержание TVP4020 PERMEDIA 2
Страница 1: ...Texas Instruments TVP4020 PERMEDIA 2 Programmer s Reference Manual Issue 4 ...
Страница 47: ...Memory I O and Organization TVP4020 Programmers Reference Manual 38 Texture address TextureBaseAddress T W S ...
Страница 284: ...TVP4020 Programmers Reference Manual A Gouraud Shaded Triangle 275 ...
Страница 292: ...TVP4020 Programmers Reference Manual Register Tables 283 ...
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Страница 315: ...Index TVP4020 Programmers Reference Manual 306 Index ...
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