Browse Prior Art Database

Header Detection Apparatus

IP.com Disclosure Number: IPCOM000100844D
Original Publication Date: 1990-Jun-01
Included in the Prior Art Database: 2005-Mar-16
Document File: 2 page(s) / 60K

Publishing Venue

IBM

Related People

Esteban, D: AUTHOR [+5]

Abstract

A technique widely used in the communication industry is the so-called "in-band-signalling" consisting in superimposing specific patterns in the main stream of data between two devices, which patterns being identified as flags for Commands or Information exchanged by both devices. For example, in a digital communication over ISDN (Integrated Services Digital Network) between two Terminal Adapters, data exchanged between terminals can be in the HDLC or SDLC (High level or Synchronous Data Link Control) format while Command or Information frames exchanged between the two Adapters feature a specific header with respect to Fig. 1. This article describes a new apparatus implemented in a Terminal Adapter to detect the header of Command or Information frames; a 10-byte (80-bit) header will be taken as an example.

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Header Detection Apparatus

       A technique widely used in the communication industry is
the so-called "in-band-signalling" consisting in superimposing
specific patterns in the main stream of data between two devices,
which patterns being identified as flags for Commands or Information
exchanged by both devices. For example, in a digital communication
over ISDN (Integrated Services Digital Network) between two Terminal
Adapters, data exchanged between terminals can be in the HDLC or SDLC
(High level or Synchronous Data Link Control) format while Command or
Information frames exchanged between the two Adapters feature a
specific header with respect to Fig. 1. This article describes a new
apparatus implemented in a Terminal Adapter to detect the header of
Command or Information frames; a 10-byte (80-bit) header will be
taken as an example.

      As shown on Fig. 2, the heart of the apparatus is a 7-bit
binary counter 1 (counts up to 128), with clock and reset inputs.
Block 2 is composed of logic associating a predefined binary value
(depending on the value of the expected header), to each one of the
80 first combinations of Q6-Q0. As long as this value is equal to the
value of incoming data, the binary counter goes on with counting.
When it reaches binary value 1010000 (80 in decimal), the output of
block 3 becomes active and the header is then detected. Otherwise,
when the output of block 2 is different from the value of incoming
data, or if the output of block 4...