B69000 Asiliant Technologies, B69000 Datasheet - Page 336

• Manufacturer Part Number: B69000
• Manufacturer: Asiliant Technologies

Specifications of B69000

• Lead Free Status / Rohs Status: Supplier Unconfirmed

BitBLT Operation
E-1
Appendix E
BitBLT Operation
Introduction
The graphics controller provides a hardware-based BitBLT engine to offload the work of moving blocks of
graphics data from the host CPU. Although the BitBLT engine is often used simply to copy a block of
graphics data from the source to the destination, it also has the ability to perform more complex functions.
The BitBLT engine is capable of receiving three different blocks of graphics data as input as shown in Figure
E-1. The source data may exist either in the frame buffer or it may be provided by the host CPU from some
other source such as system memory. The pattern data always represents an 8x8 block of pixels that must
be located in the frame buffer, usually within the off-screen portion. The input destination data is the data
already residing at the destination in the frame buffer prior to a BitBLT operation being performed. The
output destination data is the data written to the destination as a result of a BitBLT operation.
The BitBLT engine may be configured to use various combinations of the source, pattern, and input
destination data as operands, in both bit-wise logical operations to generate the output destination data. It
is intended that the BitBLT engine will perform these bit-wise and per-pixel operations on color graphics data
that is at a color depth that matches the rest of the graphics system. However, if either the source or pattern
data is monochrome, the BitBLT engine has the ability to put either block of graphics data through a process
called “color expansion” which converts the monochrome graphics data to color. Since the destination is
often a location in the on-screen portion of the frame buffer, it is assumed that any data already residing at
the destination will be of the appropriate color depth.
Figure E-1: Block Diagram and Data Paths of the BitBLT Engine
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69000 Databook
Subject to Change Without Notice
Revision 1.3 8/31/98