Data transmission system adapted to facilitate detection of safe receipt of a transmitted data frame by a receiving station

A method of transmitting signals representing a frame of data on a loop transmission path between a plurality of data stations connected to the transmission path, the steps comprising:

• generating signals representing a frame of data including a data portion, an answer information portion, a sending-station address portion and a receiving-station address portion in a first station;
• sending out said signals representing the frame of data generated in said first station to said loop transmission path from said first station;
• receiving in a second one of said stations signals representing a frame of data transmitted on said loop transmission path and immediately retransmitting the received signals representing the entire frame of data on said loop transmission path;
• comparing in said second station the address of the station with the receiving-station address portion of the frame of data received on said loop transmission path in the form of said signals to determine whether the frame of data is to be received by said second station;
• storing in said second station the signals representing said frame of data received on said loop transmission path when said comparing step indicates that the frame of data is to be received by said second station;
• checking at least the data portion of said frame of data represented by said received signals to detect abnormalities therein;
• and
• altering said received signals prior to retransmission by setting the answer information portion of the received frame of data to a selected code pattern indicating whether or not said received frame of data has been normally received in said second station [in response to] depending on the result of said checking step.

A data transmission system comprising a loop transmission path for transmitting signals representing a frame of data and a plurality of data stations connected to the transmission path and having respective addresses within the system, each of said stations comprising:

• means for generating signals representing a frame of data including a data portion, an answer information portion, a sending station address portion and a receiving-station address portion;
• means for sending out said signals representing the frame of data produced by said generating means to said loop transmission path with said data portion being positioned in advance of said answer portion;
• means for receiving signals representing a frame of data transmitted on said loop transmission path and for retransmitting the received signals representing the entire frame of data on said loop transmission path;
• means for comparing the address of the station with the receiving-station address portion of the received frame of data received in the form of said signals on said loop transmission path to determine whether the frame of data is destined for said station;
• means responsive to said comparing means for storing said signals representing at least the data portion of said received frame of data when the receiving-station address portion of said received frame of data coincides with the address of the receiving-station;
• and
• means connected to said receiving and retransmitting means for altering said received signals prior to the retransmission by setting the answer information portion of the received frame of data to one of a plurality of selected code patterns depending on at least the result of comparison by said comparing means.

A data transmission system comprising a loop transmission path for transmitting signals representing a frame of data and a plurality of data stations connected to the transmission path and having respective addresses within the system, each of said stations comprising:

• means for generating signals representing a frame of data including a data portion, a station modifiable portion, a sending station address portion and a receiving-station address portion;
• means for sending out said signals representing the frame of data produced by said generating means to said loop transmission path with said data portion being positioned in advance of said station modifiable portion;
• means for receiving signals representing a frame of data transmitted on said loop transmission path and for retransmitting the received signals representing the entire frame of data on said loop transmission path;
• means for comparing the address of the station with the receiving-station address portion of the received frame of data received in the form of said signals on said loop transmission path to determine whether the frame of data is destined for said station;
• means responsive to said comparing means for storing said signals representing at least the data portion of said received frame of data when the receiving-station address portion of said received frame of data coincides with the address of the receiving-station;
• checking means connected to said receiving and retransmitting means for checking at least the data portion of said frame of data represented by said received signals to detect abnormalities therein;
• and
• first means coupled to said checking means for setting the station modifiable portion of the received frame of data to one of a plurality of selected code patterns prior to retransmission depending on results of comparison by said comparing means and checking by said checking means.

A method of transmitting signals representing a frame of data on a loop transmission path between a plurality of data stations connected to the transmission path, the steps comprising:

• generating signals representing a frame of data including a data portion, an answer information portion, a sending-station address portion and a receiving-station address portion in a first station;
• sending out said signals representing the frame of data generated in said first station to said loop transmission path from said first station;
• receiving in a second station the signals representing a frame of data transmitted on said loop transmission path and immediately retransmitting the received signals representing the entire frame of data on said loop transmission path;
• comparing in said second station the address of the station with the receiving-station address portion of the frame of data received on said loop transmission path in the form of said signals to determine whether the frame of data is to be received by said second station;
• storing in said second station the signals representing said frame of data received on said loop transmission path when said comparing step indicates that the frame of data is to be received by said second station;
• and
• altering said received signals prior to retransmission by setting the answer information portion of the received frame of data to a selected code pattern indicating whether or not said received frame of data has been normally received in said second station.

A method of transmitting signals representing a frame of data on a loop transmission path between a plurality of data stations connected to the transmission path, the steps comprising:

• generating signals representing a frame of data including a data portion, a station modifiable portion, a sending-station address portion and a receiving-station address portion in a first station;
• sending out said signals representing the frame of data generated in said first station to said loop transmission path from said first station;
• receiving in a second one of said station signals representing a frame of data transmitted on said loop transmission path and immediately retransmitting the received signals representing the entire frame of data on said loop transmission path;
• comparing in said second station the address of the station with the receiving-station address portion of the frame of data received on said loop transmission path in the form of said signals to determine whether the frame of data is to be received by said second station;
• storing in said second station the signals representing said frame of data received on said loop transmission path when said comparing step indicates that the frame of data is to be received by said second station;
• checking at least the data portion of said frame of data represented by said received signals to detect abnormalities therein;
• and
• setting the station modifiable portion of the received frame of data prior to retransmission to a selected code pattern indicating whether or not said received frame of data has been normally received in said second station in response to the result of said checking step.

A data transmission system comprising a loop transmission path for transmitting a data frame including a sending station address field, a receiving station address field, a data field and an answer field positioned after said data field and a plurality of processors having respective addresses within the system and being connected to said transmission path and acting as either a sending side device or receiving side device, selectively, each of said processors comprising:

• means operative, when the processor acts as a sending side device, for sending out on the transmission path a data frame with an answer field having a predetermined first code pattern;
• means for receiving a data frame transmitted through the transmission path and for sending out the received data frame to the transmission path with its answer field unchanged when the processor is down;
• memory means for allowing a received data frame to be stored therein under certain conditions;
• means for comparing the address field of the received data frame with the address of the processor;
• and
• means for sending out the received data frame with its answer field changed to a predetermined second code pattern different from said first code pattern, when said comparing means indicates coincidence between the address field of the received data frame and the address of the processor and said received data frame is not allowed to be stored in said memory means, and changed to a predetermined third code pattern different from any of said first and second code patterns, when the said comparing means indicates coincidence between the address field of the received data frame and the address of the processor and said received data frame is allowed to be stored in said memory means.