Browse Prior Art Database

Hardware Rotate for Page Printers

IP.com Disclosure Number: IPCOM000100077D
Original Publication Date: 1990-Mar-01
Included in the Prior Art Database: 2005-Mar-15
Document File: 3 page(s) / 119K

Publishing Venue

IBM

Related People

Spina, WJ: AUTHOR

Abstract

Disclosed is a hardware method that uses a fast "on-chip" RAM to rotate dot matrix characters, such as the characters used by page printers.

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 52% of the total text.

Hardware Rotate for Page Printers

       Disclosed is a hardware method that uses a fast "on-chip"
RAM to rotate dot matrix characters, such as the characters used by
page printers.

      Before printing, using a rotated orientation (90o left or 90o
right), low-end page printers, such as the IBM 3812, rotate all of
the print characters.  The rotations are done in software with the
rotated characters being placed in main storage.  These rotated
characters become the font which will be used during printing.  This
software character rotation takes several seconds, as well as the new
font requiring additional memory to store.

      The hardware rotation method disclosed requires no additional
time beyond that which is required for normal (non-rotated) printing.
 Also, since the characters are rotated only as needed, no additional
memory is required.

      Fig. 1 shows a magnified character "F" rotated 90o left, normal
and rotated 90o right.  For its normal orientation, the character is
Hpel pels high and Wpel pels wide.  For rotated left or rotated
right, it is Wpel high and Hpel wide.  When the character is rotated
left 90o, its top row (left to right) becomes the leftmost column
(bottom to top).  The second row down becomes the second column over
from the left.  The next row down becomes the next column over, ...
the bottom row becomes the rightmost column.  When the character is
rotated right 90o, its top row (left to right) becomes the rightmost
column (top to bottom).  The second row down becomes the second
column over from the right.  The next row down becomes the next
column over, ... the bottom row becomes the leftmost column.

      Fig. 2 shows the hardware rotate logic.  This logic will
normally be part of a hardware assist ASIC used to support the print
processor.

      The logic consists of:
      a)   control logic,
      b)   N1 bit UP/DOWN counter that produces the RAM addresses,
   c)   N2 bit UP/DOWN counter used to control the multiplexer,
      d)   NH by NW on-chip RAM,
      e)   NW to 1 multiplexer (selects one of the NW pel columns),
f)   NW bit serial/parallel shift register (S/R) input is from the
multiplexer,
      g)   2-way selectors to select between input pel data for
normal printing and the shift register outputs for rotated printing.

      Refer to Fig. 2 for the description that follows.  The input
pel data (from the font) is written to the ASIC one word (16 bits for
present-day processors) at a time.  During normal printing, this data
is passed directly to the rasterizer ("A" inputs of the 2-way
selectors).  During rotate, the data is first written into an on-chip
static RAM.  After all Hpel rows have been written, the rotate logic
automatically generates the rotated rasteri...