Intel 815 manual Pattern Data for Example Pattern Fill BLT

Intel® 815 Chipset: Graphics Controller PRM, Rev 1.0

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Figure 20. Pattern Data for Example Pattern Fill BLT

Pattern Data

(0, 0)	(7, 0)
(0, 7)	(7, 7)

(7, 0)	(0, 0)	0
63
		100000h
		100008h
		100010h
		100018h
		100020h
		100028h
		100030h
		100038h
(7, 7)	(0, 7)

b_blt22.vsd

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.

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