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Asynchronous Data Communication System

IP.com Disclosure Number: IPCOM000060905D
Original Publication Date: 1986-May-01
Included in the Prior Art Database: 2005-Mar-09
Document File: 2 page(s) / 27K

Publishing Venue

IBM

Related People

Aoki, H: AUTHOR [+2]

Abstract

This article describes the use of a break condition (i.e., low level condition of a data transmission line with a time period equal to or longer then one character data length) to indicate the end of a block of characters. Prior asynchronous data communication systems for sending a block of characters between a sender terminal and areceiver terminal required (a) the sending of a control data indicating a length of the block or (b) the sending of ablock end code following the block of characters. However, the former requires a long transmission period and acomplicated data communication procedure to send both the control data and the block of characters.

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Asynchronous Data Communication System

This article describes the use of a break condition (i.e., low level condition of a data transmission line with a time period equal to or longer then one character data length) to indicate the end of a block of characters. Prior asynchronous data communication systems for sending a block of characters between a sender terminal and areceiver terminal required (a) the sending of a control data indicating a length of the block or (b) the sending of ablock end code following the block of characters. However, the former requires a long transmission period and acomplicated data communication procedure to send both the control data and the block of characters. The latter also requires a complicated recognition procedure for the block end code since a bit pattern of the data, when the data is an image pattern, could duplicate the pattern of the block end code. Both the approaches, therefore, are inadequate for a direct memory access data transfer scheme. To solve the problem, this article uses a brake condition of the transmission line as a block end signal, as shown in a figure. A low level condition equal to or longer than one character length is defined as the brake condition. The reason for defining such low level condition as the brake condition is that one character necessarily includes transitions between high and low levels due to start and stop bits. Then the low level condition equal to or longer than the character length...