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Parallel Port Data Bus Relay Controller Card

IP.com Disclosure Number: IPCOM000106023D
Original Publication Date: 1993-Sep-01
Included in the Prior Art Database: 2005-Mar-20
Document File: 2 page(s) / 64K

Publishing Venue

IBM

Related People

Wilding, JR: AUTHOR

Abstract

Disclosed is a circuit for the controlling of 12 relays. The circuit will monitor the parallel port data bus of a personal computer to determine which relays to switch on. A manual override is also provided for each relay. Connection for an LED indicator for each output is also provided.

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 86% of the total text.

Parallel Port Data Bus Relay Controller Card

      Disclosed is a circuit for the controlling of 12 relays.  The
circuit will monitor the parallel port data bus of a personal
computer to determine which relays to switch on.  A manual override
is also provided for each relay.  Connection for an LED indicator for
each output is also provided.

      The Parallel Port Data Bus Relay Controller monitors the
parallel port data lines of personal computer.  Data bits 0 through 5
are used for data.  Data bit 6 is used to select between two sets of
outputs.  Data bit 7 could be used to select between a third and
fourth set of outputs but that has not been done in this application.

      These data values are latched into 74373s with the -STROBE
signal from the personal computer parallel port.

      The outputs from the 74373 latches are ANDed with a manual
switch input (see connector J2S in the figure), inverted and then
driven to the output (connector J3 in the figure).

      A pull-up resistor is provided for a bank of LEDs to monitor
the current state of each output (see connector J2L in the figure).

      Following the same approach the total number of outputs
achievable through this method for a particular application is
described in the following formula:

        T = (2 sup hat A)*D

        where: T = total number of outputs possible
               A = number of data bits used for addressing
            ...