Browse Prior Art Database

MICRO CHANNEL Preempt Signal Transceiver Control

IP.com Disclosure Number: IPCOM000107515D
Original Publication Date: 1992-Mar-01
Included in the Prior Art Database: 2005-Mar-21
Document File: 2 page(s) / 57K

Publishing Venue

IBM

Related People

Fields JS, Jr: AUTHOR [+2]

Abstract

A VLSI MICRO CHANNEL* interface needs external transceivers to handle heavily-loaded control signals. The MICRO CHANNEL Fairness feature complicates control of the -PREEMPT signal transceiver. This solution avoids adding a separate VLSI output to control it. The MICRO CHANNEL (MC) Architecture defines several control signals which require a greater drive capability than a VLSI chip can provide, so external drivers are required. The -PREEMPT signal is more complicated than many of the bidirectional control signals, in that the direction is not determined solely by bus mastership. A MC adapter must always receive -PREEMPT while acting as a bus master, but when not a master, the adapter has two cases. The normal case is that the adapter will drive -PREEMPT to take away the MC from the current owner (see Fig. 1).

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 83% of the total text.

MICRO CHANNEL Preempt Signal Transceiver Control

       A VLSI MICRO CHANNEL* interface needs external
transceivers to handle heavily-loaded control signals.  The MICRO
CHANNEL Fairness feature complicates control of the -PREEMPT signal
transceiver.  This solution avoids adding a separate VLSI output to
control it.  The MICRO CHANNEL (MC) Architecture defines several
control signals which require a greater drive capability than a VLSI
chip can provide, so external drivers are required.  The -PREEMPT
signal is more complicated than many of the bidirectional control
signals, in that the direction is not determined solely by bus
mastership.  A MC adapter must always receive -PREEMPT while acting
as a bus master, but when not a master, the adapter has two cases.
The normal case is that the adapter will drive -PREEMPT to take away
the MC from the current owner (see Fig.  1).

      The other case involves Fairness.  After losing the MC, the
adapter must monitor the -PREEMPT signal until all other adapters
have ceased to drive -PREEMPT.  Once all other adapters have had a
chance to own the bus, -PREEMPT will become inactive.  This allows
the adapter that had been idle in the "Fairness Queue" to once again
drive -PREEMPT to request ownership of the MC.  This feature requires
a unique transceiver control to determine the direction of the
-PREEMPT transceiver.

      To avoid an additional VLSI output to control this transceiver,
the -BURST output can be used...