Browse Prior Art Database

Crossbar Switch Testing using Wrap Cable of Identical Carrier Technology

IP.com Disclosure Number: IPCOM000114362D
Original Publication Date: 1994-Dec-01
Included in the Prior Art Database: 2005-Mar-28
Document File: 4 page(s) / 165K

Publishing Venue

IBM

Related People

Blam, NM: AUTHOR

Abstract

Disclosed is a wrap cable device and a computer controlled method that verifies the continuity of signal paths within a crossbar switch. The wrap cable device is unique in that it is made from the same flexible technology used for the carrier in the crossbar switch. The bi-directional wrap cable is specially wired to provide all the necessary handshaking protocols for the sending and receiving ports of the switch and eliminates the need for any additional connecting cards. Computer controlled access provides for extensive transaction generation and self validation.

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Crossbar Switch Testing using Wrap Cable of Identical Carrier Technology

      Disclosed is a wrap cable device and a computer controlled
method that verifies the continuity of signal paths within a crossbar
switch.  The wrap cable device is unique in that it is made from the
same flexible technology used for the carrier in the crossbar switch.
The bi-directional wrap cable is specially wired to provide all the
necessary handshaking protocols for the sending and receiving ports
of the switch and eliminates the need for any additional connecting
cards.  Computer controlled access provides for extensive transaction
generation and self validation.

      The crossbar switch is made from a new technology called
Crossroads.  Crossroads is a flexible teflon, multi-signal
plane/multi-power plane, high pitch (20 mil) structure that can be
laminated together in the z-axis to form a multilayered (i.e.,
multi-core) assembly.  High I/O density switch wafers are soldered
onto high density substrates to form a module which is soldered onto
the top surface of the laminated switch assembly to make the crossbar
switch (Figure).

      The number of signal paths is directly related to the number of
external ports on the crossbar switch and the size of the address,
data, tag, and control busses for each port.  Because every port on
the crossbar switch must communicate with every other port by
definition, the number of communication paths within the switch logic
can be determined and is on the order of the square of the number of
ports divided by 2.  For very large bus widths on the order of 500
bits, manually verifying every possible signal path would be nearly
impossible

      With computer controlled access to the switch chips internal
logic along with the specially wired crossroads cable, the crossbar
switch can be both the source of transactions as well as the receiver
of transactions.  The transaction is initially loaded into the
receiving buffers of the switch chip logic and targets a destination
port which is connected to one end of the wrap cable.  After a known
number of system clock cycles, the transaction propagates from the
receiving buffers, thru the switch logic and arbiter, destination
port, wrap cable, and receiving port connected to the other end of
the wrap cable.  From there, the transaction is routed to a port
within the switch chip logic where system clocks are stopped and the
results verified.

      The wrap cable provides the incoming signals required by the
switch protocol.  Most of the incoming bus and control signals are
wired from the outgoing bus and control signals.  However, outgoing
transactions from the crossbar switch do not generate all the
required signals that an incoming transaction requires for a valid
transaction.  The destination id bits and priority bits are not
provided by the outgoing transaction simply because they are not
required.  In an actual switch to card configuration, there...