User's Manual

Intel® 815 Chipset: Graphics Controller PRM, Rev 1.0

Figure 20. Pattern Data for Example Pattern Fill BLT

b_blt22.vs

100000h

100008h

100010h

100018h

100020h

100028h

100030h

100038h

(0, 0)

(0, 7)

(7, 0)

(7, 7)

Pattern Data

(0, 0)(7, 0)

(0, 7)(7, 7)

As shown in figure above, the pattern data occupies 64 bytes starting at address 100000h. As always, the

pattern data represents an 8x8 array of pixels.

The BLT command packet is used to select the features to be used in this BLT operation, and must be

programmed carefully. The vertical alignment field should be set to 0 to select the top-most horizontal

row of the pattern as the starting row used in drawing the pattern starting with the top-most scan line

covered by the destination. The pattern data is in color with a color depth of 8 bits per pixel, so the

dynamic color enable should be asserted with the dynamic color depth field should be set to 0. Since this

BLT operation does not use per-pixel write-masking (destination transparency mode), this field should be

set to 0. Finally, the raster operation field should be programmed with the 8-bit value of F0h to select the

bit-wise logical operation in which a simple copy of the pattern data to the destination takes place.

Selecting this bit-wise operation in which no source data is used as an input causes the BLT engine to

automatically forego either reading source data from the frame buffer or waiting for the host processor to

provide it.

The Destination Pitch Register must be programmed with number of bytes in the interval from the start of

one scan line’s worth of destination data to the next. Since the color depth is 8 bits per pixel and the

horizontal resolution of the display is 1024, the value to be programmed into these bits is 400h, which is

equal to the decimal value of 1024.

Bits [31:3] of the Pattern Address Register must be programmed with the address of the pattern data.

Similarly, bits [31:0] of the Destination Address Register must be programmed with the byte address at

the destination that will be written to first. In this case, the address is 20080h, which corresponds to the

byte representing the pixel at coordinates (128, 128).

This BLT operation does not use the values in the Source Address Register or the Source Expansion

Background or Foreground Color Registers.

The Destination Width and Height Registers must be programmed with values that describe to the BLT

engine the 64x64 pixel size of the destination location. The height should be set to carry the value of 40h,

indicating that the destination location covers 64 scan lines. The width should be set to carry the value of

40h, indicating that each scan line’s worth of destination data occupies 64 bytes. All of this information

is written to the ring buffer using the PAT_BLT command packet.