Browse Prior Art Database

Restricted Channel Processing Logic

IP.com Disclosure Number: IPCOM000120619D
Original Publication Date: 1991-May-01
Included in the Prior Art Database: 2005-Apr-02
Document File: 2 page(s) / 61K

Publishing Venue

IBM

Related People

Andrade, RJ: AUTHOR [+7]

Abstract

This article describes the use of a simple hardware logic design to maintain "no-zero octets" integrity in integrated service digital network (ISDN) primary rate restricted data channels, instead of dedicating processing time from a digital signal processor (DSP).

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 68% of the total text.

Restricted Channel Processing Logic

      This article describes the use of a simple hardware logic
design to maintain "no-zero octets" integrity in integrated service
digital network (ISDN) primary rate restricted data channels, instead
of dedicating processing time from a digital signal processor (DSP).

      When ISDN primary rate B-channels data is to interface
connected facilities (i.e., AT&T digital trunks), these facilities
may or may not be restricted.  Restriction implies 64K bps data
traffic with the restriction per channel that if an all-zero octet is
to be transmitted, the least significant bit must be changed to a 1.
This is because, in principle, a string of 15 consecutive zeros
cannot be present on the line.  A simple solution is to use a mixture
of control logic and an array.  This article describes a simple
hardware technique that solves this problem and provides the extra
key advantage of restriction on a per-channel basis.

      Referring to the look-up table shown in the drawing, the
purpose of the table is to provide firmware with the flexibility to
assign any channel as a 64K restricted channel.  The table can have
as many channels as needed, but the example shows up to 32 channel
entries.

      Field 1 of the table is a channel-dependent single bit 64K
restricted indicator.  Information from field 1 is only for the
transmit operation of each channel.  This lookup table is loaded
during the card's initialization and can be dyna...