Browse Prior Art Database

Method and Apparatus for Parallel Communications with Local Synchronization

IP.com Disclosure Number: IPCOM000109760D
Original Publication Date: 1992-Sep-01
Included in the Prior Art Database: 2005-Mar-24
Document File: 1 page(s) / 40K

Publishing Venue

IBM

Related People

Blaum, M: AUTHOR [+2]

Abstract

An encoding and decoding apparatus for a code of rate 3/4 for use in delay-insensitive communication is disclosed. It can be used as an alternative to the rate 1/2 double-rail code assuming that there is synchronization between pairs of wires in a parallel asynchronous transmission system.

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Method and Apparatus for Parallel Communications with Local Synchronization

       An encoding and decoding apparatus for a code of rate 3/4
for use in delay-insensitive communication is disclosed.  It can be
used as an alternative to the rate 1/2 double-rail code assuming that
there is synchronization between pairs of wires in a parallel
asynchronous transmission system.

      In T. Verhoeff, "Delay-insensitive codes - an overview,"
Distributed Computing, 3:1-8, 1988, a review of coding techniques for
delay-insensitive codes in parallel asynchronous communications is
given.  The most common code used in applications is the so-called
double-rail (DR) code: a 0 is transmitted as 01, and a 1 as 10.  The
DR code is very simple to implement, which makes it attractive for
the high speeds required in parallel transmission.  However, its
drawback is that it has rate 1/2, which results in a considerable
reduction of bandwidth.

      It would be convenient to allow 11 to be a legal transmission
in each pair of wires.  In this case, we need to synchronize the
arrival of two signals for each pair.  In general, this is easily
done.  If assured that 11 is a legal message, now there is 3
possibilities for each pair of wires: 01, 10 and 11.  With two pairs
of wires, then, there is 9 possible messages.  The idea now is to
send 3 bits into (01,10,11) (01,10,11) in a 1-1 fashion.  The
resulting code will have rate 3/4, which considerably improves the
rate 1/2 DR code...