Communications link for computers

Claim 2

A communications link for a given digital computer, said link being adapted to transmit and receive over a single channel control code message and data words in series by bit to and from another computer through a like communications link associated therewith, comprising: means for receiving control code messages and data words, one at a time, from said given digital computer; means for transmitting over said channel said control code messages and data words in series by bit at a clock rate independent of cycle time of said given computer and said other computer; means for receiving control code messages and data words, one at a time, from said like communications link associated with said other computer over said channel; and means responsive to each control code message received for transmitting an appropriate one of a plurality of unique interrupt signals to said given computer except in response to a data transfer code message that data follows, and for transmitting a unique interrupt signal to said given computer in response to a data word that follows a data transfer code message.

Claim 3

A communications link as defined in claim 1 including a clock pulse generating means for use in transmitting data words and code messages, and a counter for control of said clock pulse generating means in transmitting a predetermined number of bits for a data word, and a predetermined number of bits for a code message.

Claim 4

A communications link as defined in claim 2 wherein each data word and control code message includes a parity bit, further comprising: means for checking for parity error in each code message and data word received; and error control means connected to said parity error checking means for inhibiting transmission of an interrupt signal to said given computer and for initiating transmission to said other computer through said transmitting means an error code message after a lapse of predetermined time following receipt of the first bit thereof, said time being sufficient for said like communications link associated with said other computer to complete a transmission cycle.

Claim 5

A communications link as defined in claim 3 wherein said error control means includes means for initiating transmission of an error code message after lapse of said predetermined time unless the proper number of bits have been received for a control code message or for a data word, whichever is being received, and means for counting bits received to determine when the proper number of bits have been received.

Claim 6

A communications link as defined in claim 4 wherein said transmitting means transmits binary digits in serial form as a three-level signal consisting of pulses of a given polarity for binary-1 digits, pulses of opposite polarity for binary-0 digits, and a return to zero between successive pulses.

Claim 7

A communications link as defined in claim 5 wherein said receiving means includes: means for reshaping pulses of said given polarity and omitting pulses of said opposite polarity To provide a conventional two-level signal to represent binary digits in serial form; and means for generating input clock pulses in time coincidence with pulses of both polarities, and using said input clock pulses for synchronizing the operations of receiving a code message and data word to which said pulses pertain.

Claim 8

A communications link connected to receive and transmit in parallel by bits data words from and to a given computer, and to transmit and receive serially by bit data words to and from a like communications link connected to another computer, and to receive in parallel by bits instruction words from said given computer, and to transmit and receive in series by bits control code messages, a given code message being transmitted by a given link in response to a unique instruction received by the transmitting link, comprising: means responsive to each one of said instruction words for transmitting a unique control code message to said other communications link at a clock rate independent of said given computer, a particular instruction being to transmit a particular control code message indicating that a data word is to be received thereafter in parallel from said given computer, and is to be transmitted in serial form at a clock rate independent of said given computer; means for receiving control code messages and data words, one at a time, from said like communications link in serial form; and interrupt control means responsive to each control code message received for transmitting an appropriate one of a plurality of unique interrupt signals to said given computer except in response to a control code message that data follows, and for transmitting a unique interrupt signal to said given computer in response to a data word that follows said particular control code message.

Claim 9

A communications link connected to receive and transmit in parallel by bits data words from and to a given computer, and to transmit and receive serially by bit data words to and from a like communications link connected to another computer, and to receive in parallel by bits instruction words from said given computer, and to transmit and receive in series by bits control code messages, a given code message being transmitted by a given link in response to a unique instruction received by the transmitting link, comprising: means responsive to each one of said instruction words for transmitting a unique control code message to said other communications link at a clock rate independent of said given computer, a particular instruction being to transmit a particular control code message indicating that a data word is to be received thereafter in parallel from said given computer, and is to be transmitted in serial form at a clock rate independent of said given computer; means for receiving control code messages and data words, one at a time, from said like communications link in serial form; and interrupt control means responsive to each control code message received for transmitting an appropriate one of a plurality of unique interrupt signals to said given computer except in response to a control code message that data follows, and for transmitting a unique interrupt signal to said given computer in response to a data word that follows said particular control code message.

Claim 10

A communications link as defined in claim 7 wherein transmission of control code messages and data words to and from said like communications link is over a single channel in the form of a three-level signal comprising pulses of a given polarity for binary-1 digits, pulses of opposite polarity for binary-0 digits, and a return to zero-volt level between successive pulses.

Claim 11

A communications link as defined in claim 8 including a received signal conditioning means for converting a three-level signal received into a conventional two-level signal for binary data and clock pulses on separate lines, and wherein control code messages and data words are received from said like communications link over said single channel through said signal conditions means.

Claim 12

A communications link as defined in claim 9 further comprising: error control means connected to said interrupt control means for inhibiting transmission of an interrupt signal to said given computer and for initiating transmission to said other computer through said transmitting means an error code message after a lapse of predetermined time without a full message or word being received following receipt of the first bit thereof, said time being sufficient for said like communications link associated with said other computer to complete a transmission cycle.

Claim 13

A communications link as defined in claim 10 wherein each data word and control code message includes a parity bit, further comprising: means for checking for parity error in each code message and data word received; and said error control means is responsive to said parity error checking means for inhibiting transmission of an interrupt signal from said interrupt control means to said given computer and for initiating transmission to said other computer through said transmitting means an error code message after a lapse of said predetermined time following receipt of the first bit thereof.

Claim 14

A communications link for a given digital computer, said link being adapted to transmit and receive over a single channel control code messages and data words in series by bit to and from another computer through a lIke communications link associated therewith, said digital computer having a plurality of like communications links connected thereto, comprising: means for receiving an instruction from said digital computer, said instruction having an address code uniquely identifying said communications link from other like communications link; means responsive to said instruction for transmitting over said channel a particular control code message specified by said instruction in series by bit at a clock rate independent of cycle time of said given computer and said other computer; means for transmitting over said channel a data word after a control code message has been transmitted indicating that data follows to enable the transmitting operation to take place; means for receiving control code messages and data words, one at a time, from said like communications link associated with said other computer over said channel; and means responsive to each control code message received for transmitting an appropriate one of a plurality of unique interrupt signals to said given computer except in response to a data transfer code message that data follows, and for transmitting a unique interrupt signal to said given computer in response to a data word that follows a data transfer code message.

Claim 15

A communications link for a given digital computer, said link being adapted to transmit and receive over a single channel control code messages and data words in series by bit to and from another computer through a lIke communications link associated therewith, said digital computer having a plurality of like communications links connected thereto, comprising: means for receiving an instruction from said digital computer, said instruction having an address code uniquely identifying said communications link from other like communications link; means responsive to said instruction for transmitting over said channel a particular control code message specified by said instruction in series by bit at a clock rate independent of cycle time of said given computer and said other computer; means for transmitting over said channel a data word after a control code message has been transmitted indicating that data follows to enable the transmitting operation to take place; means for receiving control code messages and data words, one at a time, from said like communications link associated with said other computer over said channel; and means responsive to each control code message received for transmitting an appropriate one of a plurality of unique interrupt signals to said given computer except in response to a data transfer code message that data follows, and for transmitting a unique interrupt signal to said given computer in response to a data word that follows a data transfer code message.

Claim 16

A communications link as defined in claim 12 including a clock pulse generating means for use in transmitting data words and code messages, and a counter for control of said clock pulse generating means in transmitting a predetermined number of bits for a data word, and a predetermined number of bits for a code message.

Claim 17

A communications link as defined in claim 13 wherein each data word and control code message includes a parity bit, further comprising: means for checking for parity error in each code message and data word received; and error control means connected to said parity error checking means for inhibiting transmission of an interrupt signal to said given computer and for initiating transmission to said other computer through said transmitting means an error code message after a lapse of predetermined time following receipt of the first bit thereof, said time being sufficient for said like communications link associated with said other computer to complete a transmission cycle.

Claim 18

A communications link as defined in claim 14 wherein said error control means includes means for initiating transmission of an error code message after lapse of said predetermined time unless the proper number of bits have been received for a control code message or for a data word, whichever is being received, and means for counting bits received to determine when the proper number of bits have been received.

Claim 19

A communications link as defined in claim 15 wherein said transmitting means transmits binary digits in serial form as a three-level signal consisting of pulses of a given polarity for binary-1 digits, pulses of opposite polarity for binary-0 digits, and a return to zero between successive pulses.

Claim 20

A communications link as defined in claim 16 wherein said receiving means includes: means for reshaping pulses of said given polarity and omitting pulses of said opposite polarity to provide a conventional two-level signal to represent binary digits in serial form; and means for generating input clock pulses in time coincidence with pulses of both polarities, and using said input clock pulses for synchronizing the operations of receiving a code message and data word to which said pulses pertain.