Cirrus Logic EP93xx - Manual (Page 266)

8-2 DS785UM1
Copyright 2007 Cirrus Logic
Graphics Accelerator
EP93xx User’s Guide
8
8
8
8.2.1 Copy
It is possible to copy data from the source memory to the destination memory using the copy
form of block transfer. A copy is accomplished by not enabling any of the data path options,
i.e. Transparency, Logical Mask, or Destination Mask.
8.2.1.1 Transparency
Transparency is used to preserve pixels in the destination memory. When a pixel in the
source block is defined as a transparent pixel, the corresponding destination pixel will be left
un-modified by the block transfer. A pixel is defined as transparent when it matches the pixel
value that is loaded into the TRANSPATTRN register. Comparisons are made based on the
bits per pixel mode of the transfer.
8.2.1.2 Logical Mask
Logical Mask is used to manipulate the pixel data as it is copied from the source location to
the destination. The source data will not be modified unless the source is also the destination.
All pixel data is manipulated based on the value of the
“BLOCKMASK” register and the
desired operation. The operations, using “C” syntax, of Logical Mask are:
AND - This operator is used to remove pattern attributes from a pixel.
Dest = BLOCKMASK & Src;
OR - This operator may be used to add regular pattern attributes to a pixel.
Dest = BLOCKMASK | Src;
XOR - This operator is used for pixel bit plane inversion.
Dest = BLOCKMASK ^ Src; (where ^ is an XOR operation)
8.2.1.3 Logical Destination
Logical Destination provides for the modification of the destination data based on the value of
the source pixels. The operations, using “C” syntax, of Logical Destination are:
AND - This operator is used to remove pattern attributes from a pixel.
Dest = Dest & Src;
OR - This operator is used to add regular pattern attributes to a pixel.
Dest = Dest | Src;
XOR - This operator is used for pixel bit plane inversion.
Dest = Dest ^ Src; (where ^ is an XOR operation)
8.2.1.4 Operation Precedence
The order of precedence is:
1. Logical Mask