Browse Prior Art Database

Improved Forms Control Using DMA And Sensor Interrupts to Reduce Processor Bandwidth

IP.com Disclosure Number: IPCOM000119316D
Original Publication Date: 1991-Jan-01
Included in the Prior Art Database: 2005-Apr-01
Document File: 2 page(s) / 89K

Publishing Venue

IBM

Related People

Leith, VS: AUTHOR [+6]

Abstract

In a typical printer application, forms control consumes approximately three to six percent of the total system processor bandwidth. However, during forms moves, this bandwidth rises considerably to approximately sixty to ninety-five percent of the processor bandwidth. The invention, described herein, would allow the forms control bandwidth requirement to be reduced to less than one percent of the total processor bandwidth, and to only three to six percent during the actual forms move.

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This is the abbreviated version, containing approximately 52% of the total text.

Improved Forms Control Using DMA And Sensor Interrupts to Reduce
Processor Bandwidth

      In a typical printer application, forms control consumes
approximately three to six percent of the total system processor
bandwidth.  However, during forms moves, this bandwidth rises
considerably to approximately sixty to ninety-five percent of the
processor bandwidth.  The invention, described herein, would allow
the forms control bandwidth requirement to be reduced to less than
one percent of the total processor bandwidth, and to only three to
six percent during the actual forms move.

      This article describes a technique for controlling forms
movement with a stepper motor and sensing a variety of influences on
the forms movement.  The description of this system is divided into
three areas:  Forms Sensing, Forms Motor Stepping and Forms Motor
Step Timing.  Each of these areas is described in the following
sections.

      FORMS SENSING To provide forms movement in an unattended
environment, several sensing requirements exist.  These requirements
are: Jam, Top of Forms, End of Forms, Paper Present and Access Cover
Open.  Typically, the state of these sensors would be polled, which
consumes a large amount of processor bandwidth.  An alternative would
be to collect the state of all these sensors, and generate a single
interrupt when a state which requires action is encountered.

      Jam sensing is particularly difficult because it is performed
by counting forms motor steps between the holes in the margin of
continuous forms.  An interrupt should not be generated unless an
excessive number of steps occurs without a forms hole moving past the
hole sensor.

      In this invention, forms steps are counted between holes.  If
an excessive number of steps is reached, an interrupt is generated.
This counter also takes into account whether a full step or a half
step is taken when generating interrupts, since twice as many half
steps occur between holes, as full steps.

      FORMS MOTOR STEPPING In order to move the forms with a stepper
motor, three operating characteristics must be known.  Th...