Communications system with error detection and retransmission

Claim 2

A data communications system for communication between a central station and a branch station said central station comprising: a. means for transmitting a message, said message comprising: i. a plurality of data words, each data word having a plurality of character bits, ii. a character parity bit associated with each data word, and iii. a message parity word associated with said pulrality of data words forming the transmitted message, b. message storage means for storing messages to be transmitted, said message storage means having a first transmit buffer and a second transmit buffer, c. status word storage means associated with said first and second buffers for storing a status word, said status word comprising: i. a first portion for indicating the data word to be transmitted in the message, ii. a second portion for indicating the message parity count for transmitted data words, said second portion indicating said message parity word upon transmission of said message, and iii. a third portion for identifying the first and second transmit buffers, d. message handling means connected to said message storage means, status word storage means, and said message transmitting means, e. message processing means connected to said message storage means for loading messages into said message storage means, f. means for receiving a positive acquisition signal and negative acquisition signal, said signal receiving means connected to said message handling means, and said branch station comprising: g. means for receiving messages from said central station, h. means for detecting bit character errors and bit message means, said error detecting means connected to said message receiving means, i. signal transmitting means for transmitting a positive acquisition signal upon the reception at said branch station of a message having neither character nor message bit errors and for transmitting a negative acquisition signal upon the detection of either a character or message bit error, said signal transmitting means connected to said error detecting means, whereby said negative acquisition signal when received in said central station causes said messages handling means to access said message storage means for retransmitting the message stored in said message storage means, and the positive acquisition signal when received in said central station permits the loading of a new message into said message storage means.

Claim 3

A data communication system as recited in claim 1 wherein said system further comprises: a. message receiving means in said central station connected to said message handling means, b. means for detecting bit character errors and bit message errors at said central station, said error detecting means of said central station connected to said message receiving means of said central station and said message handling means, c. means in said central station for transmitting a positive acquisition signal upon the reception of a message having neither character bit errors nor message bit errors, and for transmitting a negative acquisition signal upon the detection of either a character or message bit error, said signal transmitting means of said transmitting station connected to said message handling means, d. meAns in said branch station for transmitting a message, e. a message storage buffer at said branch station for storing said transmitted message of said branch station, f. message handling means in said branch station connected to the message storage buffer, the message transmitting means of said branch station and said message receiving means of said branch station, g. signal receiving means in said branch station connected to said message handling means of said branch station for receiving positive acquisition signals and negative acquisition signals from said central station, and h. terminal input means at said branch station connected to said message handling means of said branch station and said message storage buffer for loading messages into said message storage buffer, whereby said negative acquisition signal when received at said branch station causes the retransmission of the message stored in said message storage buffer, and the positive acquisition signal when received at said branch station permits the loading of new messages into said message storage buffer.

Claim 4

A data communication system as recited in claim 2 wherein said central and branch stations have data storage means connected respectively to said central and branch message handling means for storing said received messages.

Claim 5

A data communications system as recited in claim 2 wherein said branch station further comprises a presetable timing device connected to said message handling means of said branch station for causing the retransmission of the message stored in said message storage buffer when neither a positive acquisition signal nor a negative acquisition signal is received within the preset time interval.

Claim 6

A data communications system for communication between a central station and a plurality of branch stations, said central station comprising: a. means for transmitting a message, said message comprising: i. a plurality of data words, each data word having a plurality of character bits, ii. a character parity bit associated with each data word, and iii. a message parity word associated with said plurality of data words forming the transmitted message, b. a plurality of message storage means in said central station, each message storage means associated with a branch station for storing messages for transmission to each of said branch stations, each message storage means having a first transmit buffer and a second transmit buffer, c. a first plurality of status word storage means for storing status words, one status word associated with each message storage means, said status word providing an indication of the message parity count for transmitted data words, d. a message handling means connected to said plurality of message storage means, said first plurality of status word storage means and said message transmitting means, e. message processing means connected to said message storage means for loading messages into said message storage means, f. means for receiving a positive acquisition signal and negative acquisition signal, said signal receiving means connected to said message handling means, and each of said branch stations comprising: g. means for receiving messages from said central station, h. means for detecting bit character errors and bit message errors, said error detecting means connected to said message receiving means, i. signal transmitting means for transmitting a positive acquisition signal upon the reception at said branch station of a message having neither character nor message bit errors and for transmitting a negative acquisition signal upon the detection of either a character or message bit error, said signal transmitting means of said branch station connected to said error detecting means, whereby said negative acquisition signal when received in said central station from a given branch station causes said messages handling means to access said associated message storaGe means for retransmitting the message to said given branch station, and the positive acquisition signal when received in said central station from a given branch station permits the loading of a new message into said associated message storage means.

Claim 7

A data communications system for communication between a central station and a plurality of branch stations, said central station comprising: a. means for transmitting a message, said message comprising: i. a plurality of data words, each data word having a plurality of character bits, ii. a character parity bit associated with each data word, and iii. a message parity word associated with said plurality of data words forming the transmitted message, b. a plurality of message storage means in said central station, each message storage means associated with a branch station for storing messages for transmission to each of said branch stations, each message storage means having a first transmit buffer and a second transmit buffer, c. a first plurality of status word storage means for storing status words, one status word associated with each message storage means, said status word providing an indication of the message parity count for transmitted data words, d. a message handling means connected to said plurality of message storage means, said first plurality of status word storage means and said message transmitting means, e. message processing means connected to said message storage means for loading messages into said message storage means, f. means for receiving a positive acquisition signal and negative acquisition signal, said signal receiving means connected to said message handling means, and each of said branch stations comprising: g. means for receiving messages from said central station, h. means for detecting bit character errors and bit message errors, said error detecting means connected to said message receiving means, i. signal transmitting means for transmitting a positive acquisition signal upon the reception at said branch station of a message having neither character nor message bit errors and for transmitting a negative acquisition signal upon the detection of either a character or message bit error, said signal transmitting means of said branch station connected to said error detecting means, whereby said negative acquisition signal when received in said central station from a given branch station causes said messages handling means to access said associated message storaGe means for retransmitting the message to said given branch station, and the positive acquisition signal when received in said central station from a given branch station permits the loading of a new message into said associated message storage means.

Claim 8

A data communications system as recited in claim 5 further comprising: a. message receiving means in said central station connected to said message handling means, b. means for detecting bit character errors and bit message errors at said central staiton, said error detcting means of said central station connected to said message receiving means of said central station and said message handling means, c. means in said central station for transmitting a positive acquisition signal upon the reception of a message having neither character bit errors nor message bit errors, and for transmitting a negative acquisition signal upon the detection of either a character or message bit error, said signal transmitting means of said transmitting station connected to said message handling means, d. means in each branch station for transmitting a message, e. a message storage buffer at each of said branch stations for storing said transmitted message, f. message handling means in each of said branch stations connected to said message storage buffer, the message transmitting means of said branch station and the message receiving means of the branch station, g. signal receiving means in each of said branch stations connected to said message handling means of said branch station for receiving positive acquisition signals and negative acquisition signals from said central station, and h. terminal input means at each of said branch stations connected to said message handling means of said branch station and said message storage buffer for loading messages into said message storage buffer, whereby said negative acquisition signal when received at said branch station causes the retransmission of the message stored in said message storage buffer, and a positive acquisition signal when received at said branch station permits the loading of new messages into said message storage buffer.

Claim 9

A data communications system as recited in claim 6 wherein said central and each of said branch stations have data storage means connected respectively to said central and branch message handling means, for storing said received messages.

Claim 10

A data communications system as recited in claim 7 wherein said data storage means of said central station comprises a plurality of data storage means, each data storage means associated with a branch station for storing messages received from each branch station, each of said plurality of data storage means having a first receive buffer and a second receive buffer.

Claim 11

A data communications system as recited in claim 8 wherein said central station further comprises a second plurality of status word storage means connected to said message handling means of said central station, each of said second plurality of status words associated with one data storage means of said central station for providing an indication of the message parity count for received data words.

Claim 12

A data communications system as recited in claim 7 wherein each of said branch stations further comprises a presetable timing device connected to said message handling means of said branch station for causing the retransmission of the message stored in said message storage buffer when neither a positive acquisition signal nor a negative acquisition signal is received within the present time interval.