M69030 Asiliant Technologies, M69030 Datasheet - Page 383

• Manufacturer Part Number: M69030
• Manufacturer: Asiliant Technologies

Specifications of M69030

• Operating Temperature (min): 0C
• Operating Temperature Classification: Commercial
• Operating Temperature (max): 70C
• Rad Hardened: No
• Lead Free Status / Rohs Status: Supplier Unconfirmed

BitBLT Operation
E-21
Figure E-17 shows both the 8x8 pattern making up the letter “f” and how it is represented somewhere in the
host’s system memory — the actual address in system memory is not important. The letter “f” is represented
in system memory by a block of monochrome graphics data that occupies 8 bytes. Each byte carries the 8
bits needed to represent the 8 pixels in each scan line’s worth of this graphics data. This type of pattern is
often used to store character fonts in system memory.
Figure E-16: On-Screen Destination for Example Character Drawing BitBLT
Figure E-17: Source Data in System Memory for Example Character Drawing BitBLT
During this BitBLT operation, the host CPU will read this representation of the letter “f” from system memory,
and write it to the BitBLT engine by performing memory writes to the BitBLT data port. The BitBLT engine
will receive this data from the host CPU and use it as the source data for this BitBLT operation. The BitBLT
engine will be set to the same color depth as the graphics system ( 8 bits per pixel, in this case. Since the
source data in this BitBLT operation is monochrome, color expansion must be used to convert it to an 8 bpp
color depth. To ensure that the gray background behind this letter “f” is preserved, per-pixel write masking
will be performed, using the monochrome source data as the pixel mask.
As in the example of the pattern fill BitBLT operation, the first step before programming the BitBLT engine
in any way is to check either bit 0 of the BitBLT Configuration Register (XR20) or bit 31 of the BitBLT Control
Register (BR04) to see if the BitBLT engine is currently busy. After waiting until the BitBLT engine is idle,
`efmp
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69030 Databook
Revision 1.3 11/24/99