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Graphic Orders
13-6
MC68322 USER’S MANUAL
MOTOROLA
13.3.1 Physical vs Logical Address
For graphic orders that render images to frames or unbanded bit maps, the address
parameters are interpreted as physical addresses and the MC68322 uses them to access
memory directly. In the case of banded bit maps, where only a portion of the physical page’s
image may be present in memory, address parameters are interpreted as logical addresses.
The MC68322 must translate logical addresses to physical space before graphic order
execution begins. Translation information is provided to the MC68322 at the same time the
banded bitmap dimensions are defined (via the SET_BBMAP order). Physical addresses
are translated back to logical addresses when a band fault occurs, so an updated logical
address parameter can be written back to the graphic order.
13.3.2 Duplex Addresses
Based on the value of the bottom-to-top (B2T) parameter in the SET_BBMAP graphic order,
bitBLTs and scanline transfers can be rendered in a top to bottom direction for a 0
° page or
in a bottom to top direction for a 180
° page. When bit block transferring to a banded bitmap
with the B2T flag set, the definition of certain graphic order parameters change. Namely, the
frame bitmap address parameters DA, SA, and HA must be provided so they are pointing to
the bottom left corners of their respective frames (instead of the upper left) and the HYR
halftone parameter must provide the number of scanlines remaining to reach the top of the
bitmap (instead of the bottom). Figure 13-2 uses the halftone bitmap parameters to illustrate
this requirement.
The parameters of scanline operations are also affected when rendering a page from
bottom-to-top, since scanline and halftone tables must be executed in reverse order when
the B2T flag is set. DA, which normally gives the starting position for the scanline table, must
instead give the address of the pixel just beyond the last run in the scanline table. The
scanline table address, which normally points to the most-significant byte of the first bit string
specifier in the table, must instead point to the most-significant byte of the last word. In
addition, if a halftone is involved, HA, HXR, and HYR must be provided with respect to the
same pixel at the end of the image and halftone table address must point to the
most-significant byte of the last word in the halftone companion table.
Unbanded and frame bitmap operations are always rendered in top to bottom order by the
graphics unit, independent of the value of the B2T flag. Notice that for full-page duplex
applications, page images can always be rendered top-to-bottom and then printed 0
° or
180
° when rotated by the PVC. The B2T flag is important for banded duplex applications
because it allows the bands to be rendered in the reverse order as needed for delivery to
the print engine.
Note: in contrast to the order in which the print engine video controller reads an image
from memory. When the B2T bit is set in the PCB control register, the PVC reads
memory in a bottom to top, right to left order, and in doing so, produces an image
that appears rotated 180
°.
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Freescale Semiconductor, Inc.
For More Information On This Product,
Go to: www.freescale.com
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