Browse Prior Art Database

Asynchronous Communications Start And Stop Commands Control The Transmitter of UART

IP.com Disclosure Number: IPCOM000101366D
Original Publication Date: 1990-Aug-01
Included in the Prior Art Database: 2005-Mar-16
Document File: 2 page(s) / 79K

Publishing Venue

IBM

Related People

Krantz, JI: AUTHOR [+4]

Abstract

This article describes a technique for use in a computer system wherein a start transmit and a stop transmit command is added to an universal asynchronous receiver transmitter (UART) to allow special control characters to be inserted into the data stream.

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 52% of the total text.

Asynchronous Communications Start And Stop Commands Control The Transmitter of UART

       This article describes a technique for use in a computer
system wherein a start transmit and a stop transmit command is added
to an universal asynchronous receiver transmitter (UART) to allow
special control characters to be inserted into the data stream.

      Asynchronous adapters for some computer systems implement an
interrupt mode to service the transmitter data requests. However, if
a direct memory access (DMA) mode was implemented with communications
controllers on these adapters, the insertion of characters becomes
difficult. Both the transmitter and the DMA controller would have to
be disabled.  Then the transmitter would be initialized for interrupt
mode to handle the insertion of multiple characters.  Also, the
initialization of the transmitter to interrupt mode would affect the
receiver.  Once the inserted characters are transmitted the
communication controller would have to be reinitialized to DMA mode
before transmission could resume.  The technique disclosed herein
allows a user to send start and stop commands to control an
asynchronous communications transmitter.  Once the transmitter is
stopped, the user is able to insert and transmit multiple control
characters in the middle of first-in, first-out (FIFO) or DMA chained
data stream.

      The UART is an electronic chip which takes bytes of data from a
computer's data channel and hands them one bit at a time to a serial
communications channel, such as a telephone line.  The chip also
provides service in the reverse direction by collecting bits from a
phone line and handing them to the computer a byte at a time.

      The U...