Browse Prior Art Database

Generation of Bus Signals -Preempt And Arb(0-3) for Micro Channel Architecture

IP.com Disclosure Number: IPCOM000101297D
Original Publication Date: 1990-Jul-01
Included in the Prior Art Database: 2005-Mar-16
Document File: 2 page(s) / 71K

Publishing Venue

IBM

Related People

Ingles, RJ: AUTHOR [+2]

Abstract

This article describes a circuit arrangement which generates the correct timing in a personal computer system for the -PREEMPT and ARB(0-3) signals so that an adapter (not shown) can arbitrate for use of the MICRO CHANNEL* bus.

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 53% of the total text.

Generation of Bus Signals -Preempt And Arb(0-3) for Micro Channel Architecture

       This article describes a circuit arrangement which
generates the correct timing in a personal computer system for the
-PREEMPT and ARB(0-3) signals so that an adapter (not shown) can
arbitrate for use of the MICRO CHANNEL* bus.

      The circuit disclosed herein is shown in the drawing. Internal
card signal -BUSREQ will go active (low) indicating that a bus access
is requested.  If the adapter is not in the inactive state and has
not already been granted the bus, -PREEMPT will be driven active
(low).  When the adapter has been granted the bus, the signal MATCH
will go active (high).  MATCH is generated by comparing the ARBO -
ARB3 lines of the bus to the ARB ID of the adapter.

      The adapter can request access to the bus at any time, but must
not be allowed to arbitrate for it if an arbitration cycle is in
progress (ARB/-GNT is high). -PREEMPT will be driven active, as
described above, when -BUSREQ goes active even if an arbitration
cycle is in progress.  If it is in progress, the adapter will not
arbitrate (i.e., drive the adapter ARB IDs onto the bus), but will
activate -PREEMPT, and continue to do so until the adapter has been
granted the bus.

      The signal LPRE, generated by flip-flop U1, is used to
determine when to drive the ARB IDs onto the bus.  Normally, the
adapter drives -PREEMPT active and the system responds with an
arbitration cycle (ARB/-GNT go...