AMD Geode LX 800@0.9W - Manual (Page 284)

284 AMD Geode™ LX Processors Data Book
Display Controller 33234H
Cursor/Icon Buffer Formats
In 2-bpp mode, the cursor buffer is stored as a linear dis-
play buffer containing interlaced AND and XOR QWORDs
(8-byte segments). Each QWORD contains the appropriate
mask for 64 pixels. Even QWORDs contain the AND
masks and odd QWORDs contain the XOR masks. The
masks are stored “in display order” with the leftmost pixel
being most significant and the rightmost pixel being least
significant.
For 32-bpp cursors, the cursor pixels include an alpha
value, and are alpha blended with the underlying graphics
pixels. For the purposes of cursor overlay, the cursor alpha
value is used. If the graphics stream includes an alpha
value, that value is not used for the purposes of cursor
overlay. However, the graphics alpha value is retained in
the resulting pixel stream.
The cursor buffer stores 192 bytes of data per scan line (for
48 horizontal pixels) in 32-bpp mode. In this mode, the cur-
sor size is 48 pixels wide and 64 pixels high, and so the
buffer is 12 KB in size.
In 2-bpp mode, cursor buffer includes 16 bytes of data per
scan line (for 64 horizontal pixels). The cursor is 64x64,
therefore the cursor buffer is 1 KB in size.
The DC contains logic to address the overlay of the cursor
on top of a color key region. Table 6-35 indicates what pixel
value is output from the DC’s rendering engine when the
cursor is overlayed on the color key region.
Note that this behavior varies slightly when the graphics
are represented in 32-bpp mode, which includes a per-
pixel alpha value.
Table 6-35. Cursor/Color Key/Alpha Interaction
Cursor Per-Pixel Alpha
Color Key Match, Per-
Pixel Alpha
No Per-Pixel Alpha
Color Key Match, No
Per-Pixel Alpha
No Cursor COLOR = graphics
color
ALPHA = graphics
alpha
COLOR = graphics
color
ALPHA = 00
COLOR = graphics
color
ALPHA = FF
COLOR = graphics
color
ALPHA = 00
2-bpp Cursor
(cursor color) COLOR = cursor color
ALPHA = graphics
alpha or FF (config-
urable)
COLOR = cursor color
ALPHA = FF
COLOR = cursor color
ALPHA = FF
COLOR = cursor color
ALPHA = FF
2-bpp Cursor
(invert color) COLOR = invert graph-
ics color
ALPHA = graphics
alpha or FF (config-
urable)
COLOR = invert
graphics color
ALPHA = FF
COLOR = invert
graphics color
ALPHA = FF
COLOR = invert
graphics color
ALPHA = FF
2-bpp Cursor
(transparent) COLOR = graphics
color
ALPHA = graphics
alpha
COLOR = graphics
color
ALPHA = 00
COLOR = graphics
color
ALPHA = FF
COLOR = graphics
color
ALPHA = 00
Color Cursor
(with alpha) COLOR = blend cur-
sor/graphics
ALPHA = pp alpha or
FF (configurable)
COLOR = cursor color
ALPHA = cursor alpha
COLOR = blend
cursor/graphics
ALPHA = FF
COLOR = cursor color
ALPHA = cursor alpha