Dismiss
InnovationQ will be updated on Sunday, Oct. 22, from 10am ET - noon. You may experience brief service interruptions during that time.
Browse Prior Art Database

Two Way Communications Procedure Using a Single UART

IP.com Disclosure Number: IPCOM000121869D
Original Publication Date: 1991-Oct-01
Included in the Prior Art Database: 2005-Apr-03
Document File: 2 page(s) / 68K

Publishing Venue

IBM

Related People

Blair, BE: AUTHOR

Abstract

A single universal asynchronous receiver transmitter (UART) is simultaneously operated as a secondary station on one communications link and a primary station on another communications link by taking advantage of the characteristics of a polled, multi-point communications environment. The benefit of this procedure is lower system cost by using one UART instead of two to perform this function.

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

Two Way Communications Procedure Using a Single UART

      A single universal asynchronous receiver transmitter
(UART) is simultaneously operated as a secondary station on one
communications link and a primary station on another communications
link by taking advantage of the characteristics of a polled,
multi-point communications environment.  The benefit of this
procedure is lower system cost by using one UART instead of two to
perform this function.

      For the purpose of describing this procedure, a communications
system is defined such that station 1 originates data for station 2
to process and then forward to station 3.  Station 2 is a secondary
station on the link controlled by station 1 and station 3 is a
secondary station on the link controlled by station 2.  In addition,
station 3 can originate data to be sent back through station 2 to
station 1.  A primary station "polls" a secondary station, i.e., the
primary station only allows the secondary station to send data
messages when the secondary station has received a poll message from
the primary station.  The "poll message" allows the secondary station
a window of time during which the secondary station can have control
of the communications link to send data back to the primary station.

      Normally, using a single UART at station 2 to redrive data to
station 3 would cause problems because while the UART was sending or
receiving data with station 3 it could not simultaneously service the
communications interface to station 1.

      However, taking advantage of the nature of a polled system, the
following algorithm allows a single UART at station 2 to meet all
communication requirements with both station 1 and station 3.
Case 1 - Station 2 receiving a data...