US 4,377,862 A · Method of error control in asynchronous communications

Abstract

Error control, in the form of a modulo 2 division remainder checksum is added to a packet of reformatted asynchronous characters prior to transmission over a data link connecting two data devices such as a host computer and a teletype terminal. At one end of the link, data in asynchronous form, such as ASCII code, comprising seven data bits, start and stop bits, and a parity bit, is originated by one data device. The start, stop and parity bits of each character are eliminated. The remaining data bits for a selected number of characters are then grouped together to form a data grouping and the checksum and other control information bits added, forming an information packet. The information packet is then divided into sections or groups of eight bits. Start and stop bits are added to each group, forming ten bit characters. The ten bit characters are then transmitted over the data link in standard asynchronous format. The process is carried out in reverse at the other end of the link, resulting in the other data device receiving the data in the form originated by the first data device. Sophisticated error control techniques thus may be implemented in asynchronous communications without detrimentally affecting the data capacity of the channel.

Claims26

Dependent claims

An asynchronous digital data communication system for use with two digital data communication stations, both adapted to operate asychronously with digital characters made up of first control bits and a predetermined number of data bits, comprising:

a first terminal and a second terminal operable with the two stations, respectively, and means operatively associated with said first terminal and said second terminal providing a communication channel therebetween;
said first terminal including station input means operable with one station for asynchronously receiving a first character therefrom and combining only the data bits of said first character with string control bits to form a first information bit string, section means operatively associated with said station input means for dividing said first information bit string into sections, each having a number of bits equal to one or more than said predetermined number, and channel output means operatively associated with said section means for adding section control bits to each section to form a digital word, and then asynchronously transmitting said digital word via said communication channel;
said second terminal including channel input means operatively associated with said communication channel for asynchronously receiving said digital word and then removing said section control bits therefrom to form a second information bit string, reformatting means operatively associated with said channel input means for combining only the data bits of said second information bit string with second control bits identical to said first control bits to form a second character identical to said first character, and station output means operatively associated with said reformatting means and operable with the other station for asynchronously presenting said second character to said other station.

a first terminal and a second terminal operable with the two stations, respectively, and means operatively associated with said first terminal and said second terminal providing a communication channel therebetween, each terminal including;
(A) FOR TRANSMITTING TO THE OTHER TERMINAL--station input means operable with one station for asynchronously receiving a first character therefrom and combining only the data bits of said first character with string control bits to form a first information bit string, section means operatively associated with said station input means for dividing said first information bit string into sections, each having a number of bits equal to one more than said predetermined number, and channel output means operatively associated with said section means for adding section control bits to each section to form a digital word, and then asynchronously transmitting said digital word via said communication channel;
and
(B) FOR RECEIVING FROM THE OTHER TERMINAL--channel input means operatively associated with said communication channel for asynchronously receiving said digital word and then removing said section control bits therefrom to form a second information bit string, reformatting means operatively associated with said channel input means for combining only the data bits of said second information bit string with second control bits identical to said first control bits to form a second character identical to said first character, and station output means operatively associated with said reformatting means and operable with the other station for asynchronously presenting said second character to said other station.

1 more element

A terminal for presenting digital words to a communication channel and operable with a digital data communication station that is adapted to operate asychronously with digital characters made up of first control bits and a predetermined number of data bits, the terminal comprising:

(A) FOR TRANSMITTING--station input means operable with the station for asynchronously receiving a first character therefrom and combining only the data bits of said first character with string control bits to form a first information bit string;
section means operatively associated with said station input means for dividing said first information bit string into sections, each having a number of bits equal to one more than said predetermined number;
channel output means operatively associated with said section means for adding section control bits to each section to form a digital word, and then asynchronously presenting said digital word to the communication channel;
and
(B) FOR RECEIVING--channel input means operatively associated with the communication channel for asynchronously receiving said digital word and then removing said section control bits therefrom to form a second information bit string;
reformatting means operatively associated with said channel input means for combining only the data bits of said second information bit string with second control bits identical to said first control bits to form a second character identical to said first character;
and
station output means operatively associated with said reformatting means and operable with the station for asynchronously presenting said second character to said station.

5 more elements

A method for asynchronous digital data communication for use with two digital data communication stations both adapted to operate asychronously with digital characters made up of first control bits and a predetermined number of data bits, the method comprising the steps of:

asynchronously receiving a first character from one station;
combining only the data bits of said first character with string control bits to form a first information bit string;
dividing said first information bit string into sections, each having a number of bits equal to one more than said predetermined number;
adding section control bits to each section to form a digital word;
asynchronously transmitting said digital word;
asynchronously receiving said digital word and then removing said section control bits thereform to form a second information bit string;
combining only the data bits of said second information bit string with second control bits identical to said first control bits to form a second character identical to said first character;
and
asynchronously presenting said second character to the other station.

6 more elements

(A) FOR TRANSMITTING--
asynchronously receiving a first character from one station;
combining only the data bits of said first character with string control bits to form a first information bit string;
dividing said first information bit string into sections, each having a number of bits equal to one more than said predetermined number;
adding section control bits to each section to form a digital word;
asynchronously transmitting said digital word;
(B) FOR RECEIVING--asynchronously receiving said digital word, and then removing said section control bits therefrom to form a second information bit string;
combining only the data bits of said second information bit string with second control bits identical to said first control bits to form a second character identical to said first character;
and
asynchronously presenting said second character to the other station.

7 more elements

A method for asynchronous digital data communication for use with a digital data communication station adapted to operate asychronously with digital characters made up of first control bits and a predetermined number of data bits, the method comprising the steps of:

(A) FOR TRANSMITTING--
asynchronously receiving a first character from the station;
combining only the data bits of said first character with string control bits to form a first information bit string;
dividing said first information bit string into sections, each having a number of bits equal to one more than said predetermined number;
adding section control bits to each section to form a digital word;
asynchronously transmitting said digital word;
(B) FOR RECEIVING--asynchronously receiving said digital word, and then removing said section control bits therefrom to form a second information bit string;
combining only the data bits of said second information bit string with second control bits identical to said first control bits to form a second character identical to said first character;
and
asynchronously presenting said second character to the station.

7 more elements

Dependencies are inferred from the claim text.

Method of error control in asynchronous communications

Life of this patent

Method of error control in asynchronous communications

Life of this patent

Abstract

Claims26