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Browse Prior Art Database

Asynchronous Digital Video Switching System

IP.com Disclosure Number: IPCOM000102063D
Original Publication Date: 1990-Oct-01
Included in the Prior Art Database: 2005-Mar-17
Document File: 7 page(s) / 257K

Publishing Venue

IBM

Related People

Farrell, RH: AUTHOR [+2]

Abstract

An asynchronous digital switching system is described which enables several data sources to be transmitted simultaneously to various destinations. The concept is particularly adaptable to interconnection requirements of video/computer subsystems which require high connectivity and bandwidth between elements.

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 27% of the total text.

Asynchronous Digital Video Switching System

       An asynchronous digital switching system is described
which enables several data sources to be transmitted simultaneously
to various destinations.  The concept is particularly adaptable to
interconnection requirements of video/computer subsystems which
require high connectivity and bandwidth between elements.

      Typically, video transmission requires a high bandwidth at a
relatively constant rate.  The expansion of transmission
capabilities, to include the simultaneous transmission of digital
data, generally requires bandwidth and connectivity enhancements.
Therefore, the concept described herein provides an asynchronous
digital video switching system enabling multiple unidirectional
connections between inputs and outputs.

      The concept utilizes several unique features not found in other
video switching systems, as follows:
 1. The switch enhances switching flexibility such that it permits
reserved or non-reserved routing within the same switch.  The normal,
or non-reserved, connection, when in a reject mode, will cause the
source to be removed.  The normal mode allows all sources to
arbitrate for the destination path when it becomes available.  The
alternate, or reserved mode, method of connection when rejected
enables the source to maintain an active mode in order to reserve the
path for transmission as soon as routing is available.
 2. Permits broadcasting of data through the switch.  This allows an
input to transmit its data to several, or all, destinations
simultaneously.  The input simply specifies all of the destinations
in the routing control to selectively access multiple destinations.
Typically, this is done in the reserved mode where the switch will be
in reject mode until all requested destinations are available for
broadcast.
 3. Provides the ability to cascade ports together so as to increase
the data path width through the same input.

      The controls for the additional cascaded ports are disabled and
controlled by way of the base port.  This allows the switch to be
used in applications requiring even higher bandwidth between the
inputs and outputs.  An N x N switch with byte-wide data paths is
reconfigured as an N/2 x N/2 switch with sixteen bit data paths.
This is accomplished by tieing down an input to the switch.  This
input being low causes port 2 to be cascaded as an extension to port
1 forming a sixteen-bit port. Port 4 is cascaded with port 3, etc.

      Fig. 1 illustrates the implementation of the asynchronous
digital video switch in the receiving and transmitting of byte-wide
data at each port.  The switch is designed to provide self-routing in
that the switch receives path selection commands over the same
byte-wide interface that is used for data transfer operations.  Fig.
2 illustrates a typical 4x4 switch with receive input ports Rx and
output ports Tx.  No data buffering or data clocking is required.
Data passes t...