Initialization
TVP4020
Programmers Reference Manual
136
lbWindowBase = lbBaseA
(lbWidth * (lbHeight-1-600) + 200)
LBWindowBase(lbWindowBase)
Where fbBaseAddress, fbWidth and fbHeight are the physical base
address, width and height of the framebuffer (in pixels). fbBaseAddress
and lbBaseAddress will have been precomputed as described in Section
§6.2.6. As with the WindowOrigin data, if the window moves, these
registers must be updated.
6.3.3
Writemasks
Normally both the hardware (if present) and the software writemasks will
initially be set to make all bitplanes writeable:
FBSoftwareWriteMask(PERMEDIA_ALL_WRITEMASKS_SET)
FBHardwareWriteMask(PERMEDIA_ALL_WRITEMASKS_SET)
6.3.4
Enabling Writing
Which buffers are enabled at any given time is window specific and
should be considered for performance reasons. Performance will be
improved if unnecessary reads from, and writes to, buffers are disabled.
For example if the current rendering does not use depth or stencil testing
then reading and writing to the localbuffer may be disabled. The
following example initializes the buffers to allow depth buffering and
alpha blending:
fbWriteMode.UnitEnable = PERMEDIA_ENABLE
FBWriteMode(fbWriteMode)
lbWriteMode.UnitEnable = PERMEDIA_ENABLE
LBWriteMode(lbWriteMode)
lbReadMode.ReadSourceEnable = PERMEDIA_DISABLE
lbReadMode.ReadDestinationEnable = PERMEDIA_ENABLE
LBReadMode(lbReadMode)
fbReadMode.ReadSourceEnable = PERMEDIA_DISABLE
fbReadMode.ReadDestinationEnable = PERMEDIA_ENABLE
FBReadMode(fbReadMode)
Note that to use software writemasking, the FBReadMode register's
ReadDestinationEnable field will need to be set if the writemask is set to
other than all 1's.
6.3.5
Setting Pixel Size
The size of the pixels must be set so that the memory can be accessed
correctly. To do this, use the FBReadPixel register e.g.:
Содержание TVP4020 PERMEDIA 2
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