Browse Prior Art Database

Card-Presence Card and Ring Bus Failure Detection

IP.com Disclosure Number: IPCOM000117038D
Original Publication Date: 1995-Dec-01
Included in the Prior Art Database: 2005-Mar-31
Document File: 4 page(s) / 129K

Publishing Venue

IBM

Related People

Aureglia, JJ: AUTHOR [+5]

Abstract

In the context of a machine made of several I/O adapter cards which port connect to workstations. The purpose of this machine is to provide workstations switching, in other words, to allow switched connections to be established and released between the workstations; this is performed by a special microprocessor card running a dedicated software. Different I/O adapter cards exist supporting different number of ports and different speeds.

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 52% of the total text.

Card-Presence Card and Ring Bus Failure Detection

      In the context of a machine made of several I/O adapter cards
which port connect to workstations.  The purpose of this machine is
to provide workstations switching, in other words, to allow switched
connections to be established and released between the workstations;
this is performed by a special microprocessor card running a
dedicated software.  Different I/O adapter cards exist supporting
different number of ports and different speeds.

      The machine is built around a ring Bus running on a backplane.
Microprocessor and I/O adapter cards may be plugged onto the ring Bus
at any slot position.  When the machine is powered on, the
microprocessor card should automatically discover its configuration
to initialize the switching system.

      During configuration discovery, the microprocessor polls each
ring Bus slot where a potential I/O adapter card may exist and
expects an answer back from the card providing its type, status and
port configuration.  Since this is a ring Bus, this answer should
make its way back to the microprocessor card by following the ring.

When no response is received from a poll, the microprocessor should
then make the difference between:
  1.  No I/O card is installed in the corresponding slot
  2.  I/O card is the corresponding slot but is not operational
  3.  I/O card is installed and operational but the ring Bus is no
       longer operational.

      In the first case, it might be perfectly right not to have an
I/O card in this slot and initialization can continue normally.  In
the second case, an alarm has to be reported to the operator to
signal that the card is not operational.  The last case is more
likely to occur when the machine is made of multiple stackable boxes
and the ring Bus goes through the backplane of each of these boxes.
And in this case, the failure location should be isolated to trigger
an easy and fast repair action.  Hereafter is described a very simple
and unexpensive logic to provide the means to differentiate between
the above three conditions.

      As seen in Fig. 1, the backplane the ring Bus has one wire used
for reporting the I/O adapter card presence and operational
indications; it is called the ACK line.

      On the microprocessor card there is a latch called the ACK
latch its setting is made when the ACK line is negated.  The
microprocessor can reset and test this latch.

Each card connector has a wire wrapping an input signal to the ACK
line; this input signal may be triggered by two different logics:
  The Card Presence (CP) logic
  The Command Decode (CD) logic

On the backplane...