M69000 Asiliant Technologies, M69000 Datasheet - Page 351

• Manufacturer Part Number: M69000
• Manufacturer: Asiliant Technologies

Specifications of M69000

• Lead Free Status / Rohs Status: Supplier Unconfirmed

E-16
As is shown in Figure E-12, there are four bytes allocated for each pixel on each scan line’s worth of pattern
data, which allows each scan line’s worth of 24bpp pattern data to begin on a 32-byte boundary. The extra
(“fourth”) unused bytes of each pixel on a scan line’s worth of pattern data are collected together in the last
8 bytes (the last quadword) of each scan line’s worth of pattern data.
Bit 18 of the BitBLT Control Register (BR04) specifies whether the pattern data is color or monochrome.
The various bit-wise logical operations and per-pixel write-masking operations were designed to work with
color data. In order to use monochrome pattern data, the BitBLT engine is designed to convert it into color
through a process called “color expansion” which takes place as a BitBLT operation is performed. In color
expansion, the single bits of monochrome pattern data are converted into one, two, or three bytes
(depending on the color depth to which the BitBLT engine has been set) of color data that are set to carry
values corresponding to either the foreground or background color that have been specified for use in this
process. The foreground color is used for pixels corresponding to a bit of monochrome pattern data that
carry the value of 1, while the background color is used where the corresponding bit of monochrome pattern
data carries the value of 0. The foreground and background colors used in the color expansion of
monochrome pattern data can be set in the Pattern/Source Expansion Foreground Color Register (BR02)
&+,36
69000 Databook
Figure E-11: 16bpp Pattern Data -- Occupies 128 Bytes (16 Quadwords)
Figure E-12: 24bpp Pattern Data -- Occupies 256 Bytes (32 Quadwords)
Subject to Change Without Notice
BitBLT Operation
Revision 1.3 8/31/98