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Resolution Converter for Page Printers Disclosure Number: IPCOM000101983D
Original Publication Date: 1990-Oct-01
Included in the Prior Art Database: 2005-Mar-17
Document File: 4 page(s) / 178K

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Booth, JR: AUTHOR [+3]


Disclosed is a hardware method that converts input data streams that are not 300 dots per inch into 300 dots per inch.

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 37% of the total text.

Resolution Converter for Page Printers

       Disclosed is a hardware method that converts input data
streams that are not 300 dots per inch into 300 dots per inch.

      The print resolution used by many laser printers, such as the
IBM LaserPrinter, is fixed at 300 dots per inch (DPI) both
horizontally and vertically.  In order for these printers to be
general purpose, they must be able to accept data streams that were
generated for printers having other resolutions.  For example:  A
block of graphics data designed for a printer with a resolution of
240 DPI would, if printed at 300 DPI without conversion, be distorted
(reduced in size).  If the data conversion was done totally in
software, the printer throughput (pages per minute) would be reduced
as well as more memory being required since a larger portion of the
bitmap would have to be processed prior to starting the print engine.
This disclosure describes a method to convert data of various
resolutions into 300 DPI such that the printer will operate at normal
throughput with no distortion.

      Of the two conversions:  horizontal and vertical, the
horizontal requires the most processor time.  In this article, a
hardware horizontal conversion is described.  The vertical conversion
can be done without effecting throughput in software and will not be
described.  Horizontal is defined here as across the paper in the
8-1/2-inch direction regardless of the orientation of the image on
the page.

      HORIZONTAL CONVERSION A circuit (contained in an ASIC) is
provided which, when given a word of input data (16 bit wide data
will be used for the description) of some resolution, will produce an
output whose resolution is 300 DPI.  The circuit consists of digital
logic gates which are controlled by a microprocessor and software
which cause the image to be printed on the paper.

      RESOLUTION CONVERTER Resolution conversion is the process where
source data is expanded or reduced to 300 DPI from some other (or the
same) resolution.  The hardware has twelve modes which provide for
conversion of different resolutions (60 to 360 DPI) of source data to
300 DPI at the target.  See the figure at the end of this article for
details on the various resolutions and the expansion/ contraction
patterns used. The MODE register contains four bits to select which
of these modes is to be used.  On each write, the source data will be
converted as dictated by the pattern type.  Note that the converter
is ALWAYS in use; if no change in resolution is desired, set the mode
to 1:1 (MODE = 0).  For the bit definition of the MODE and PAT
registers, see the figure.

      Some modes have more than one pattern to use for the conversion
rules.  The PAT register contains three bits to select which pattern
is to be used.  When the target resolution is not evenly divisible
into (or by) 300 DPI, multiple patterns are necessary to represent a
target bit stream without discontinuities w...