Browse Prior Art Database

Improvement On Parallel Arbitration Scheme

IP.com Disclosure Number: IPCOM000120144D
Original Publication Date: 1991-Mar-01
Included in the Prior Art Database: 2005-Apr-02
Document File: 2 page(s) / 61K

Publishing Venue

IBM

Related People

Wright, CG: AUTHOR

Abstract

Disclosed is an improvement on a well-known parallel arbitration scheme that has been used on various microcomputer data buses, notably, the IBM Microchannel. The scheme described here has completely distributed control and is implemented using only four wires.

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 61% of the total text.

Improvement On Parallel Arbitration Scheme

      Disclosed is an improvement on a well-known parallel
arbitration scheme that has been used on various microcomputer data
buses, notably, the IBM Microchannel. The scheme described here has
completely distributed control and is implemented using only four
wires.

      In the parallel arbitration scheme, ownership of the bus is
determined by a distributed priority scheme in which all potential
bus owners compete for the bus during an arbitration period. This
scheme is well known, so it will not be described here.

      The invention being disclosed here uses the same mechanism for
determining the next bus owner. It differs in its means for control
of the process. In this scheme, the current bus owner remains owner
until it sees a request by some other device. The current owner, at
completion of its activity, defines a competition period during which
the potential new owners arbitrate among themselves for use of the
bus. At the end of the competition period, the new owner is
determined.

      The arbitration scheme is implemented using four wires, as
shown in Fig. 1. Three of these are arbitration/request lines. During
the competition period, they are used to resolve future bus
ownership.  Otherwise, they are used to indicate a request to use the
bus. The fourth wire is a "COMPETE" line, driven by the current bus
owner to indicate the period of competition for future bus ownership.

      Fig. 2 illustrat...