M69000 Asiliant Technologies, M69000 Datasheet - Page 292

• Manufacturer Part Number: M69000
• Manufacturer: Asiliant Technologies

Specifications of M69000

• Lead Free Status / Rohs Status: Supplier Unconfirmed

14
13
12
11
10
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Color Transparency Enable
Monochrome Source Write-Masking
Source Color Depth
Reserved (Writable)
Source Select
69000 Databook
These bit is used to enable or disable color transparency.
When color transparency is enabled, the color value carried within bits 23-0 of either BR01
or BR09 is used as a key color to mask the writing of pixel data to the destination on a per-
pixel basis. Before each pixel at the destination is written, a comparison is made between
this key color and another color, and whether or not that given pixel at the destination will
actually be written depends upon the result of that comparison.
Whether BR01 or BR09 is used to supply the key color depends on the setting of bit 27 of
BR03 since the same register that is used to supply the key color for color transparency
also happens to be used to supply the background color for monochrome-to-color
expansion. Also, depending on the type of color transparency selected via bits 16-15 of
this register, the other color value to which the key color is compared may be the color value
resulting from the bit-wise operation selected via bits 7-0 of this register.
0: Disables color transparency.
1: Enables color transparency.
Note: Color transparency can be used only when the BitBLT engine is set to a color depth
of 8 or 16 bits per pixel, but not 24 bits per pixel. If the BitBLT engine has been set to a
color depth of 24 bits per pixel, then this bit should always remain set to 0 to disable color
transparency.
Note: This bit applies only when the source data is monochrome (determined by bit 12 of
this register).
This bit enables a form of per-pixel write-masking in which monochrome source data is
used as a pixel mask that controls which pixels at the destination will be written to by the
BitBLT engine.
0: This disables the use of monochrome source data as a write mask, allowing normal
operation of the BitBLT engine with regard to the use of monochrome source data.
1: Wherever a bit in monochrome source data carries the value of 0, the byte(s) of the
corresponding pixel at the destination are NOT written, thereby preserving any data already
carried by those bytes.
0: Specifies that the source data is in color, and therefore, can have a color depth of 8, 16,
or 24 bits per pixel.
1: Specifies that the source data is monochrome, and therefore, has a color depth of 1 bit
per pixel. This setting should be used only if bit 8 of this register is set to 0.
Note: This bit must be set to 0 whenever a bit-wise operation is selected (using bits 7-0 of
this register) that does not use source data.
This bit should always be written with the value of 0.
0: Configures the BitBLT engine to read the source data from the frame buffer at the
location specified in BR06.
1: Configures the BitBLT engine to accept the source data from the host CPU via the
BitBLT data port. The host CPU provides the source data by performing a series of
memory write operations to the BitBLT data port.
Subject to Change Without Notice
BitBLT Registers
Revision 1.3 8/31/98
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