Browse Prior Art Database

Nine Bit Command/Data Protocol for RS232 Async

IP.com Disclosure Number: IPCOM000108975D
Original Publication Date: 1992-Jul-01
Included in the Prior Art Database: 2005-Mar-23
Document File: 1 page(s) / 42K

Publishing Venue

IBM

Related People

Henson Jr, JD: AUTHOR [+4]

Abstract

Disclosed is a method of sending one extra bit with each byte transmitted to indicate the nature of the byte as command or data. This extends existing hardware to a more flexible protocol. This Nine-Bit Command/Data Protocol for RS232 Async performs the function without modifying existing hardware or extending transmit/receive overhead.

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This is the abbreviated version, containing approximately 81% of the total text.

Nine Bit Command/Data Protocol for RS232 Async

       Disclosed is a method of sending one extra bit with each
byte transmitted to indicate the nature of the byte as command or
data.  This extends existing hardware to a more flexible protocol.
This Nine-Bit Command/Data Protocol for RS232 Async performs the
function without modifying existing hardware or extending
transmit/receive overhead.

      Applications using Standard Async communications for Personal
Computers cannot differentiate between data and command bytes easily
without reserving special patterns.  Additionally, standard RS232
Async communications on personal computers are limited to eight bit
bytes, which is the basic data unit of the machine.

      When attempting to process an incoming data stream, it may be
necessary to differentiate between basic data and command or status
information.  Unless a portion of the range of input values possible
is dedicated to specific usage as command or status indicators or the
receiving program knows the numbers of incoming bytes to interpret as
data, there appears to be no way to determine the type of byte
received.  If specific input values are dedicated to command or
status indicators, the range of data values are restricted and
special steps must be taken to handle data whose value conflicts with
commands.  If a data length is either implied or explicit in the
protocol, the ability to asynchronously notify the receiver of status
changes may be lost. ...