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Browse Prior Art Database

Hardware Dot Option Generation for Serial Printers

IP.com Disclosure Number: IPCOM000121034D
Original Publication Date: 1991-Jul-01
Included in the Prior Art Database: 2005-Apr-03
Document File: 6 page(s) / 275K

Publishing Venue

IBM

Related People

Jenkins, SK: AUTHOR [+4]

Abstract

In most serial printer applications, some means of detecting the position of the printhead is required. In this embodiment, the position detection is provided by a two-channel encoder mounted on the drive shaft of a DC motor, which is connected to the printhead via a drive band. In a typical application, the encoder outputs, known as emitters, are filtered and then used to both control the printhead speed and provide timing information for firing the printhead. Since a two-channel encoder is used and each channel is 90 degrees out of phase with the other channel, known as quadrature, it is also possible to determine printhead direction. An example of such a mechanism controller can be found in Fig. 1.

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 27% of the total text.

Hardware Dot Option Generation for Serial Printers

      In most serial printer applications, some means of
detecting the position of the printhead is required.  In this
embodiment, the position detection is provided by a two-channel
encoder mounted on the drive shaft of a DC motor, which is connected
to the printhead via a drive band. In a typical application, the
encoder outputs, known as emitters, are filtered and then used to
both control the printhead speed and provide timing information for
firing the printhead.  Since a two-channel encoder is used and each
channel is 90 degrees out of phase with the other channel, known as
quadrature, it is also possible to determine printhead direction.  An
example of such a mechanism controller can be found in Fig. 1.

      This mechanism controller takes the quadrature emitter pulses
from the printhead motor encoder and filters them with an emitter
processor.  This processor examines the two-channel emitter pulse
stream and determines the direction of rotation of the printhead
motor, which determines the direction of printhead travel.  In
addition, the emitter processor generates a reduced resolution
position increment, which is used by the printhead motor controller
to both control the speed of the printhead motor and to generate
timing pulses which correspond with possible dot positions on the
media to be printed, known as dot options.

      Since the printhead is traveling at some velocity while it is
printing, the timing of these dot options must be compensated for the
velocity of the printhead.  These dot options provide the printhead
drivers with the necessary timing information to allow printing.
When these dot options are combined with the printhead data, printing
is produced.  In addition to generating dot options, the printhead
motor controller, as its name implies, must also control the speed of
the printhead motor.  The speed of this motor is controlled by
adjusting the voltage applied to it.  Since the printhead motor can
be operated in either direction, a voltage polarity must also be
provided.  These two quantities are then supplied to the printhead
motor driver, which physically drives the motor.
Dot Option Processor Interface

      An improvement to this system would off-load the responsibility
of dot option generation to a logic circuit known as a dot option
processor.  This dot option processor provides the printhead motor
controller with a more accurate inter-emitter time than was
previously achievable, while off-loading the requirement for dot
option generation.  In order to generate dot options the dot option
processor requires the printhead motor controller to provide it with
certain characteristics of the printhead operation.  These
characteristics include:  velocity, position and pel density.  An
example of this improved system can be seen in Fig. 2.

      Velocity compensation is communicated to the dot option
processor in the form of...