Browse Prior Art Database

Semifair Arbiter for Bus Communication

IP.com Disclosure Number: IPCOM000117527D
Original Publication Date: 1996-Mar-01
Included in the Prior Art Database: 2005-Mar-31
Document File: 2 page(s) / 47K

Publishing Venue

IBM

Related People

Chung, VE: AUTHOR

Abstract

Disclosed is a bus arbitration method which favors high priority devices on the bus but also avoids starvation of lower priority devices. This bus arbitration is very fast and simple to implement.

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 60% of the total text.

Semifair Arbiter for Bus Communication

      Disclosed is a bus arbitration method which favors high
priority devices on the bus but also avoids starvation of lower
priority devices.  This bus arbitration is very fast and simple to
implement.

      The semifair arbiter is used to arbitrate access to a bus with
multiple devices attached.  This logic can be used on any general bus
arbiter.  This invention simplifies the arbiter design by using an
algorithm that is not totally fair, but would prevent lock-out or
starvation of any device which wants to access the bus.

      The semifair arbiter requires one bit memory element for each
device on the bus which in combination forms the sampling registers.
This arbiter operates as follows:
  a) The sampling register is a free running sampling the request
      lines from each device.  This register is zero if no requests
are
      pending.  The sampling will stop once this register is
non-zero,
      meaning that one or more devices has requested access to the
bus.
      This is called the arbitration snapshot cycle.
  b) The arbiter will then proceed to grant access to the bus
starting
      with the least significant bit.  Once the grant is accepted,
the
      arbiter will reset this bit and continue to grant another
request
      if there are more bits set.
  c) Once all bits are reset, the arbitration snapshot is completed
      and the register will continue its fr...