Browse Prior Art Database

Disabling the ARTRY_ and SHD_ Precharge on a System Bus Interface

IP.com Disclosure Number: IPCOM000112543D
Original Publication Date: 1994-May-01
Included in the Prior Art Database: 2005-Mar-27
Document File: 2 page(s) / 30K

Publishing Venue

IBM

Related People

Arroyo, RX: AUTHOR [+4]

Abstract

Disclosed is a solution to the problem of precharging the ARTRY_ and SHD_ pins on a system bus interface. These pins may be driven by more than one source at a time, presenting a problem in a mixed technology environment.

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Disabling the ARTRY_ and SHD_ Precharge on a System Bus Interface

      Disclosed is a solution to the problem of precharging the
ARTRY_ and SHD_ pins on a system bus interface.  These pins may be
driven by more than one source at a time, presenting a problem in a
mixed technology environment.

      In a mixed technology environment with some 3.6 V devices and
some 5.0 V devices, a problem can arise when precharging the ARTRY_
and SHD_ pins.  These signals are active low, and so the precharge is
driving high.  The system bus is TTL compatible, so the high state
may go as high as 5.0 V.  For the 3.6 V devices, this causes a
problem.  Once the Once the voltage rises slightly over 3.6 V, these
devices will reverse their current direction, and large amounts of
current will flow from the 5.0 V devices to the 3.6 V devices.  Over
time, this causes an electro-migration reliability problem.

      One solution to this problem is to have a disable function for
the precharge in all devices that exist on the bus interface.  In
systems without mixed technology, the precharge occurs as originally
specified, so no changes are necessary.  In systems that have mixed
technology, the disable function would be used and one central source
would be responsible  for providing the precharge after every
ARTRY_/SHD_ window.