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Browse Prior Art Database

Automatic Baud Detection Implemented in CMOS Logic

IP.com Disclosure Number: IPCOM000107755D
Original Publication Date: 1992-Mar-01
Included in the Prior Art Database: 2005-Mar-22
Document File: 6 page(s) / 252K

Publishing Venue

IBM

Related People

McMillan, GW: AUTHOR

Abstract

Described is an automatic baud detection hardware implementation in complementary metal oxide semiconductor (CMOS) logic that allows applications with large terminal cluster configurations to perform an auto baud function with a high degree of accuracy. A hardware solution is introduced as opposed to a software solution, so as to improve the accuracy and reduce the number of retries prevalent in prior art.

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This is the abbreviated version, containing approximately 31% of the total text.

Automatic Baud Detection Implemented in CMOS Logic

       Described is an automatic baud detection hardware
implementation in complementary metal oxide semiconductor (CMOS)
logic that allows applications with large terminal cluster
configurations to perform an auto baud function with a high degree of
accuracy.  A hardware solution is introduced as opposed to a software
solution, so as to improve the accuracy and reduce the number of
retries prevalent in prior art.

      Automatic baud (autobaud) detection is a feature that is common
in multiplexer and asynchronous terminal controllers.  The detection
feature permits the terminal controller to communicate with a
terminal at the correct baud rate by automatically detecting the
terminal's baud rate.  This is done without resorting to multiple
iterations of setting terminal speed switches.

      Autobaud detection also permits different terminals operating
at different rates to access a multiplexer via a dial network.  Since
it is not known which terminal will come into which multiplexer
channel, it is impossible to set the speed of the channels in
advance.  Therefore, the multiplexer must adapt to each terminal rate
as the calls are answered.

      In prior art, algorithms were used to accomplish the autobaud
detection.  A terminal would send a special predetermined and pre-
configured character.  This character, usually a carriage return
(CR), would then be detected and decoded by the terminal controller,
or multiplexer, to determine the speed of the terminal that sent it.
The implementation of this detection feature, in prior art, was
implemented in software where the code must tightly sample the
different bit components of the autobaud character and then perform a
software algorithm to determine the actual speed in bits per second.
However, the software implementation presented performance and
accuracy problems in applications where the input/output (I/O)
processor terminal controllers were configured to drive terminal
clusters of up to sixty-four terminals.  At the same time, the
controllers were called upon to perform higher levels of
communication subsystem protocol functions.

      The concept described herein is designed to reduce the
aforementioned software accuracy and performance problems by
implementing the autobaud detection feature in hardware. This enables
the I/O processor terminal controller to be fully configured so as to
be able to perform higher level protocol functions and to guarantee
accurate autobaud detection functions by implementing the algorithm
totally in hardware.  Software is not requested to perform any
algorithms.

      The autobaud detection implementation in CMOS logic performs
character recognition.  The circuitry can be customized to recognize
one or more characters for the purpose of determining the network
clock pulses.   The only requirement is that there be at least two
transitions, a transition being a '1' to a...