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Test for a Twinaxial Work Station Controller Multiplexer/Demultiplexer

IP.com Disclosure Number: IPCOM000107190D
Original Publication Date: 1992-Jan-01
Included in the Prior Art Database: 2005-Mar-21
Document File: 6 page(s) / 277K

Publishing Venue

IBM

Related People

Dancker, GA: AUTHOR

Abstract

For a Work Station Controller (WSC) that is multiplexing 2 to 8 ports over a single twinaxial cable or a pair of fiber-optic cables, it is important that the WSC, the demultiplexer, and the fiber optic cable between the two, can be thoroughly tested. This article describes two tests: 1) A stand-alone self-test to verify the operation of the demultiplexer, and 2) A wrap test that can verify the operation of the WSC, the demultiplexer, and the cable between the two, and help with problem isolation to the failing unit. This wrap test is initiated by the WSC and does not require any wrap plug or other changes to the normal way that these units are connected.

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Test for a Twinaxial Work Station Controller Multiplexer/Demultiplexer

       For a Work Station Controller (WSC) that is multiplexing
2 to 8 ports over a single twinaxial cable or a pair of fiber-optic
cables, it is important that the WSC, the demultiplexer, and the
fiber optic cable between the two, can be thoroughly tested.  This
article describes two tests: 1) A stand-alone self-test to verify the
operation of the demultiplexer, and 2) A wrap test that can verify
the operation of the WSC, the demultiplexer, and the cable between
the two, and help with problem isolation to the failing unit.  This
wrap test is initiated by the WSC and does not require any wrap plug
or other changes to the normal way that these units are connected.

      Figs. 1 and 2 show the connection of a multiplexing Work
Station Controller (WSC), an 8-port demultiplexer, and the attached
cable(s).

      To help with problem determination, it is important to be able
to test each component of the above network.  WSC diagnostic code
verifies the WSC operation, a self-test of the demultiplexer verifies
its operation, and finally, a WSC - cable - demultiplexer wrap test
verifies the entire network.  This article describes the self-test of
the demultiplexer and the wrap test that can verify the operation of
all three units.

      This self-test is initiated by doing the following:
      1.  Power off the demultiplexer.
      2.  If fiber-optic cables are used between the WSC and the
demultiplexer, disconnect these at the demultiplexer.  If twinaxial
cable is used here, it does not have to be disconnected.
      3.  Connect an optical fiber from the demultiplexer optical
driver to the demultiplexer optical receiver.
      4.  Set the Self-Test switch to on.
      5.  Power on the demultiplexer.

      The demultiplexer will continue looping through its self-test
until the Self-Test switch is turned off or until power is turned
off.  Turning the Self-Test off while power is on to the
demultiplexer returns the demultiplexer to its normal mode of
operation.

      This test checks out the following circuitry in the
demultiplexer:
      1.  Serializer logic.
      2.  All 8 twinaxial port drivers and receivers.
      3.  Fiber-Optic transmitter.
      4.  Fiber-Optic receiver.
      5.  Deserializer.
      6.  Port Address frame parity checker.
      7.  Data integrity (data loaded into the serializer is compared
to the data received by the deserializer).

      The self-test checks out the circuits indicated with an '**'
next to them in Figs. 3 and 4.

      Fig. 5 shows the data patterns that are used for the self-test.
The data pattern that is used consists of a start of transmission
pattern, followed by a port address frame, followed by a single frame
containing a poll command. This data pattern is sent to each port
(port address frame is changed from 000 to 001...