Browse Prior Art Database

Bus Arbitration Using a Future Bus Owner Queue

IP.com Disclosure Number: IPCOM000105622D
Original Publication Date: 1993-Aug-01
Included in the Prior Art Database: 2005-Mar-20
Document File: 2 page(s) / 55K

Publishing Venue

IBM

Related People

Fuhs, RE: AUTHOR [+3]

Abstract

Described is a method for eliminating unnecessary dead cycles, between bus transmissions, by using a Future Bus Owner Queue.

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 57% of the total text.

Bus Arbitration Using a Future Bus Owner Queue

      Described is a method for eliminating unnecessary dead cycles,
between bus transmissions, by using a Future Bus Owner Queue.

      The bus described, uses a central arbitor, located on one of
the devices attached to the bus.

      To avoid unnecessary delay between bus operations, we designed
the arbitration logic to issue multiple "Bus Grants".  All bus units
queue the "Bus Grants" in a Future Bus Owner Queue (a FIFO queue).
The bus arbitor ensures that the number of outstanding "Bus Grants"
is not greater than the size of the Future Bus Owner Queue.

      When a bus operation begins, each bus unit removes the oldest
queue entry (the current bus owner), and shifts the queue by one.
Then each bus unit examines the oldest entry in the Future Bus Owner
Queue, to determine if it is the next bus owner.  If so, it will take
ownership of the bus (by driving the "Owned" line active, and issuing
its command) as soon as the current operation is completed ("Owned"
deactivated), without having to wait for a "Bus Grant", which could
arrive several cycles, after the current operation is done.

      An arbitration cycle can occur on any cycle, as long as the
Future Bus Owner Queue is not full.  If the Future Bus Owner Queue is
full, then the arbitor must wait for the start of a new bus operation
(which will cause the oldest queue entry to be removed from the
queue), before it can issue another "Bus Grant", wh...