Intel 815 Manuel D’Utilisation
Intel® 815 Chipset: Graphics Controller PRM, Rev 1.0
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6.3.2.
Drawing Characters Using a Font Stored in System Memory
In this example BLT operation, a lowercase letter “f” is to be drawn in black on a display with a gray
background. The resolution of the display is 1024x768, and the graphics system has been set to a color
depth of 8 bits per pixel.
background. The resolution of the display is 1024x768, and the graphics system has been set to a color
depth of 8 bits per pixel.
Figure 22.
On-Screen Destination for Example Character Drawing BLT
63
b_blt12.vsd
0
128, 128
20080h
(128th Scan Lin
(128th Scan Lin
20480h
(129th Scan Lin
(129th Scan Lin
20880h
(130th Scan Lin
(130th Scan Lin
20C80h
(131th Scan Lin
(131th Scan Lin
21080h
(132nd Scan Lin
(132nd Scan Lin
21480h
(133rd Scan Lin
(133rd Scan Lin
21880h
(134th Scan Lin
(134th Scan Lin
21C80h
(135th Scan Lin
(135th Scan Lin
Scan Lines 128 Through 135
Destination
(135, 135)
128, 128
Note: Drawing is not to scale
(0, 0)
(0, 767)
(1023, 0)
(1023, 767)
135, 135
The figure above shows the display on which this letter “f” is to be drawn. As shown in this figure, the
entire display has been filled with a gray color. The letter “f” is to be drawn into an 8x8 region on the
display with the upper left-hand corner at the coordinates (128, 128).
entire display has been filled with a gray color. The letter “f” is to be drawn into an 8x8 region on the
display with the upper left-hand corner at the coordinates (128, 128).
Figure 23.
Source Data in System Memory for Example Character Drawing BLT
b_blt13.vsd
0
63
57 56
48 47
40 39
24 23
32 31
16 15
8 7
Pixel (0, 0)
Pixel (0, 7)
Pixel (7, 0)
Pixel (7, 7)
00000000 00010000 00010000 00111100 00010000 00010000 00001100 00000000
(0, 7) (7, 7)
(7, 0) (0, 0)
Source Data
The figure above shows both the 8x8 pattern making up the letter “f” and how it is represented
somewhere in the host’s system memory — the actual address in system memory is not important. The
letter “f” is represented in system memory by a block of monochrome graphics data that occupies 8
bytes. Each byte carries the 8 bits needed to represent the 8 pixels in each scan line’s worth of this
graphics data. This type of pattern is often used to store character fonts in system memory.
somewhere in the host’s system memory — the actual address in system memory is not important. The
letter “f” is represented in system memory by a block of monochrome graphics data that occupies 8
bytes. Each byte carries the 8 bits needed to represent the 8 pixels in each scan line’s worth of this
graphics data. This type of pattern is often used to store character fonts in system memory.
During this BLT operation, the host processor will read this representation of the letter “f” from system
memory, and write it to the BLT engine by performing memory writes to the ring buffer as an immediate
memory, and write it to the BLT engine by performing memory writes to the ring buffer as an immediate