B69000 Asiliant Technologies, B69000 Datasheet - Page 353

• Manufacturer Part Number: B69000
• Manufacturer: Asiliant Technologies

Specifications of B69000

• Lead Free Status / Rohs Status: Supplier Unconfirmed

E-18
BitBLT Operation
BitBLT Programming Examples
Pattern Fill -- A Very Simple BitBLT
In this example, a rectangular area on the screen is to be filled with a color pattern stored as pattern data
in off-screen memory. The screen has a resolution of 1024x768 and the graphics system has been set to
a color depth of 8 bits per pixel.
As shown in Figure E-13, the rectangular area to be filled has its upper left-hand corner at coordinates (128,
128) and its lower right-hand corner at coordinates (191, 191). These coordinates define a rectangle
covering 64 scan lines, each scan line’s worth of which is 64 pixels in length — in other words, an array of
64x64 pixels. Presuming that the pixel at coordinates (0, 0) corresponds to the byte at address 00h in the
frame buffer memory, the pixel at (128, 128) corresponds to the byte at address 20080h.
Figure E-13: On-Screen Destination for Example Pattern Fill BitBLT
As shown in Figure E-14, the pattern data occupies 64 bytes starting at address 100000h. As always, the
pattern data represents an 8x8 array of pixels.
Before programming the BitBLT engine in any way, bit 0 of the BitBLT Configuration Register (XR20) or bit
31 of the BitBLT Control Register (BR04) should be checked to see if the BitBLT engine is currently busy.
The BitBLT engine should not be programmed in any way until all BitBLT operations are complete and the
BitBLT engine is idle. Once the BitBLT engine is idle, programming the BitBLT engine for the operation in
this example should begin by making sure that the BitBLT Configuration Register (XR20) is set to 00h, in
order to specify a color depth of 8 bits per pixel and enable normal operation. Alternatively, if bit 23 of the
BitBLT Control Register (BR04) is set to 1, then the color depth of the BitBLT engine may be set to 8 bits
per pixel by setting bits 25 and 24 of the same register to 0, although it is still necessary to ensure that at
least bit 1 of the BitBLT Configuration Register is set to 0 to enable normal operation.
The BitBLT Control Register (BR04) is used to select the features to be used in this BitBLT operation, and
must be programmed carefully. Bits 22-20 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. Since actual pattern data will be used, bit 19 should be set to 0. The pattern data is in color
with a color depth of 8 bits per pixel, so bits 18 and 17 should also be set to 0. Since this BitBLT operation
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69000 Databook
Subject to Change Without Notice
Revision 1.3 8/31/98