Browse Prior Art Database

Multi-Speed Infrared Subsystem

IP.com Disclosure Number: IPCOM000117498D
Original Publication Date: 1996-Mar-01
Included in the Prior Art Database: 2005-Mar-31
Document File: 4 page(s) / 169K

Publishing Venue

IBM

Related People

Hartley, L: AUTHOR [+3]

Abstract

Disclosed is a method for communication between enabled computers through a variety of Infrared communications protocol standards through a protocol independent programming interface. The hardware disclosed implements transparency functions that abstract the details of the specific communication channel speed and modulation from the host computers.

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 36% of the total text.

Multi-Speed Infrared Subsystem

      Disclosed is a method for communication between enabled
computers through a variety of Infrared communications protocol
standards through a protocol independent programming interface.  The
hardware disclosed implements transparency functions that abstract
the details of the specific communication channel speed and
modulation from the host computers.

      The Multi-Speed Infrared Subsystem is an architecture for
Infrared communication between enabled computers through the Infrared
Data Association (IrDA) standard.  This standard defines a physical
channel modulation architecture for various speeds as well as Link
Access & Management software protocols.  The evolution of the
different speeds of standard IrDA communication (9600-115200
bits/sec, 1.152 Mbits/s & 4.000 Mbits/s) have brought with each of
them physical channel modulation differences required for acceptable
link behavior.  The impact of these channel differences has been to
require software to be closely involved with the transmission and
reception of data through the medium.  Different communication speeds
requiring different software driver protocols to properly process
data prior to transmission and following reception.  The Multi-speed
Infrared Subsystem supports 1.6us Serial Infrared Mode, 1.152 HDLC
Mode and 4Mbit Fast Infrared Mode in a transparent manner.

      1.6 MS Serial Infrared Mode

      This mode is used by communicating stations for 'negotiation'
in IrDA communication.  In this mode units exchange ID's and
communication capabilities which define each units supported
protocols.  This mode runs data at UART rates from 2400baud to
115200baud.

      In the transmitted data stream, '0's are represented by a 1.6
MS pulse of transmitted IR and '1's in the data stream are
represented by no transmitted IR.  The asynchronous bitwise protocol
used by the UART  ensures syncronization is maintained between
transmitter and receiver by  the ensured presence of '0's in the data
stream.

      The means for packetizing data through the UART is done by
an intensive software algorithm involving the stuffing of additional
control bytes into the data stream to delimit data.  The software
manipulation that performs this is called 'transparency mode' whereby
control bytes that appear in the data stream are made 'transparent'
by additional control character insertion.  The multi-speed Infrared
Subsystem is architected to allow software to eliminate this compute
intensive operation and instead simply issue the unmodified packet to
the hardware for transmission.  If the active communication mode is
1.6us Serial Infrared Mode, the transparency operation will be
handled by the hardware at both the transmit and receive sides of the
communication link.

      1.152Mbit IBM Mode

      This protocol is Synchronous Data Link Control (SDLC) based.
The modulation is the same as HP mode except that the presence of...