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Browse Prior Art Database

Open-Line Control System

IP.com Disclosure Number: IPCOM000102481D
Original Publication Date: 1990-Nov-01
Included in the Prior Art Database: 2005-Mar-17
Document File: 2 page(s) / 41K

Publishing Venue

IBM

Related People

Knauft, G: AUTHOR [+3]

Abstract

In many cases, CMOS logic chips have logic inputs which are used only for some chip applications and have to be kept at a defined static logic level for others. For applications where the configuration can change (e.g., by plugging additional cards), a solution is required which keeps the logic input in a defined state, if there is no driver on the net, and which allows a driver, if existing, to change the state of the net.

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 100% of the total text.

Open-Line Control System

       In many cases, CMOS logic chips have logic inputs which
are used only for some chip applications and have to be kept at a
defined static logic level for others.  For applications where the
configuration can change (e.g., by plugging additional cards), a
solution is required which keeps the logic input in a defined state,
if there is no driver on the net, and which allows a driver, if
existing, to change the state of the net.

      A solution to the problem is shown in the drawing.  A receiver
is used which keeps the input signal line latched by a weak feedback
on the receiver until a driver changes the line level.  The receiving
chip comprises a driver on the same signal line.  This is typically
true for standard logic products, such as gate arrays, where all I/O
pins are connected to a configurable bidirectional I/O cell.

      In the initialization phase, the driver is activated for a
short time after power-on to set the input line to a defined state
and then reset to high Z.  Subsequently, the latching receiver keeps
the line in that state.  If the signal is functionally employed
during the operation phase, the driver of the chip driving the signal
controls the latter after power-on.