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RS422/449 In Service Error Injector Test Set

IP.com Disclosure Number: IPCOM000110184D
Original Publication Date: 1992-Sep-01
Included in the Prior Art Database: 2005-Mar-25
Document File: 2 page(s) / 96K

Publishing Venue

IBM

Related People

Giordano, LJ: AUTHOR

Abstract

Disclosed is a circuit that is designed to be an in-service logic error injector for the RS422 interface. The unit is capable of inserting logic errors singularly or continuous at two different rates into a live RS422 data stream. One of the key technical features of this device is its ability to pass data until an error is inserted by the user.

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RS422/449 In Service Error Injector Test Set

       Disclosed is a circuit that is designed to be an
in-service logic error injector for the RS422 interface.  The unit is
capable of inserting logic errors singularly or continuous at two
different rates into a live RS422 data stream.  One of the key
technical features of this device is its ability to pass data until
an error is inserted by the user.

      The error injection is accomplished by taking advantage of the
electrical characteristics of the RS422 interface, more specifically,
the use of differential signalling, which is also commonly referred
to as the balanced mode of data transmission.  In the balanced mode,
the binary value depends on the direction of the voltage path and
each signal on the interface is represented by a twisted pair.  The
lines in the pair are designated as lines 'A' and 'B'.  So, for
example, inbound data may be designated as RxD(A) and RxD(B).  To
accomplish error injection, the inbound data is first connected to a
2-to-1 Mux, as illustrated in Fig. 1.  The control signal will choose
which of the two differential signals will be present on the output
Y.  The output is then connected to an RS449 Driver, which then
generates a new differential signal, based on the output of the Mux
(Y).  Errors are introduced into the signal path by momentarily
selecting the 'B' portion of the inbound data.  The selection control
of the mux is therefore carefully controlled, and, as expected,...