Browse Prior Art Database

Circuitry to Reduce Contention Effects On Bidirectional Nets

IP.com Disclosure Number: IPCOM000102153D
Original Publication Date: 1990-Oct-01
Included in the Prior Art Database: 2005-Mar-17
Document File: 2 page(s) / 48K

Publishing Venue

IBM

Related People

Borkenhagen, J: AUTHOR [+4]

Abstract

Described is a method to transfer control on a bidirectional bus that gives optimum performance without affecting reliability.

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 89% of the total text.

Circuitry to Reduce Contention Effects On Bidirectional Nets

       Described is a method to transfer control on a
bidirectional bus that gives optimum performance without affecting
reliability.

      The reliability and performance problems created by contention
are solved with a driver design that has separate drive and hold
circuitry.  The drive circuitry has high current output capability
that is used to quickly charge a net to a valid voltage level.  The
hold circuitry has low current output capability and is used to hold
the net at a valid voltage level.  The current output of the hold
circuitry is only large enough to react to induced noise and any
leakage current on the net.  The outputs of the drive and hold
circuitry are connected together to drive a net in parallel.

      Separate enables exist for the drive and hold circuitry.  The
enable for the drive circuitry is activated at the start of a cycle
and is only active long enough to charge the net to a valid voltage
level.  The enable for the hold circuitry is activated at the start
of the cycle and remains active until the net data is sampled.  The
drive and hold circuitry have a common data input.  A logic diagram
of the driver is shown in Fig. 1.

      When imperfect tracking between driver control logic causes
contention, the driver getting off the net will have only its hold
circuitry active.  The low current capability of the hold circuitry
elimi nates reliability concerns creat...