Data transmission system and method for transmitting data having real-time and non-real-time characteristics

• US 5,430,843 A
• Filed: 07/26/1994
• Issued: 07/04/1995
• Est. Priority Date: 02/16/1987
• Status: Expired due to Fees

• Current Assignee: Kabushiki Kaisha Toshiba (Toshiba Corporation), Toshiba Corporation
• Original Assignee: Kabushiki Kaisha Toshiba (Toshiba Corporation)
• Inventors: Idemori, Kimito, Sato, Tadashi
• Primary Examiner(s): Black, Thomas G.
• Assistant Examiner(s): Von Buhr, Maria N.
• Application Number:
  US08/279,868
• Time in Patent Office: 343 Days
• Field of Search: 395/200, 395/275, 395/325, 364/DIG. 1, 364/DIG. 2
• US Class Current: 709/225
• CPC Class Codes: H04L 12/417 with deterministic access, e.g. token passing
• CPC Class Codes: H04L 12/64 Hybrid switching systems
• CPC Class Codes: H04L 12/6418 Hybrid transport
• CPC Class Codes: H04L 2012/6435 Bus
• CPC Class Codes: H04L 2012/6451 Deterministic, e.g. Token, DQDB

Abstract

A system for transmitting data between a plurality of linked stations within a cycle period defined by successive transmissions of a header signal indicating the start of a data transmission, only one station having a right to transmit data at a given time, the data including a first portion for which real-time characteristics are required, and a second portion for which real-time characteristics are not required. Each station includes a transmission circuit for transmitting the header signal and the data to another station, a receiver circuit for receiving the header signal and the data from another station, and a control circuit for assigning the right to transmit data serially to each station in a prescribed order two times within each cycle period and for transmitting the first portion of the data separately from the second portion of the data. The first portion of the data is transmitted the first time that the right to transmit data is assigned to the station.

Claims

1. A system for transmitting data between N linked stations, where N is greater than 2, one of which is designated a master station, within a cycle period defined as a period between successive transmissions of a header signal indicating a start of data transmission by the N linked stations, only one station having a right to transmit data at a given time, the data transmitted by each station including a first portion for which real-time characteristics are required, and a second portion for which real-time characteristics are not required, each Mth station (1<

=M<

=N) comprising;

transmission means for transmitting a header signal to another station when the station including the transmission means is designated a master station, and for transmitting ones of both the first and second data portions to another station,

receiver means for receiving a header signal and first and second data portions transmitted from another station, and

control means, coupled to the transmission means and the receiver means, for assigning to the station including the control means the right to transmit data in a cycle period, wherein the cycle period is divided into 2N time slots, and wherein data is transmitted by the control means only in at least one of a first time slot constituting an Mth time slot, and a second time slot constituting an N+Mth time slot within the cycle period and for transmitting the first portion of the data separate from transmission of the second portion of the data, the first portion being transmitted by the transmission means in the first time slot and the second portion being transmitted by the transmission means in the second time slot, wherein the control means is able to transmit data only in the first and second time slots.

2. The system of claim 1, wherein only one of the plurality of linked stations at a time is designated a master station, and wherein the control means includes means for generating the header signal when the right to transmit data is reassigned to the master station after the second portion of the data has been transmitted by the master station.

3. The system of claim 1, wherein the control means includes timer means for generating a timing signal after a prescribed time from a preselected starting point during a cycle period, and inhibition means for inhibiting the transmission of data from the station including the control means.

4. The system of claim 3, wherein the first and second data portions are transmitted in frames of predetermined size, and the control means also includes means responsive to the receiver means for permitting data transmission by the station only when a number of frames of predetermined size received by the station reaches a preset number and the prescribed time has not elapsed.

5. The system of claim 4, wherein the control means includes means for counting the number of frames received by the station after receipt of the header signal, and means for generating a permission signal when the number of frames counted by the counting means reaches the preset number.

6. The system of claim 5, wherein the control means also includes data control means for separating the data into the first portion and the second portion.

7. The system of claim 6, wherein the control means includes means for resetting the counting means in response to receipt of the header signal.

8. The system of claim 4, wherein the control means includes dummy frame means for determining when there is no data to be transmitted and for transmitting a frame containing no data both when the right to transmit data is assigned to the station and there is no data to be transmitted by the station, and when data transmission is inhibited by the inhibition means.

9. The system of claim 4, wherein the control means also includes substitute frame means responsive to the receiver means for determining when no frame is received by the receiver means for a predetermined time and for transmitting a frame containing no data when no frame is received by the receiver means for a predetermined time.

10. The system of claim 9, wherein the substitute frame means includes a frame timer for measuring the predetermined time and a substitute frame sending circuit responsive to the frame timer for generating the substitute frame.

11. A method of transmitting data, including a first portion for which real-time characteristics are required and a second portion for which real-time characteristics are not required, between a plurality of N linked stations, where N is greater than 2, the data being transmitted from one station to at least one other station within a cycle period defined as a period between successive transmissions of a header signal indicating a start of transmission, the method comprising the steps of:

assigning a right to transmit data by circulating the data transmission right among the N linked stations in a prescribed order;

dividing the cycle period into 2N time slots, such that each of the N linked stations is assigned a data transmission right during first and second time slots during each cycle period;

transmitting a header signal from a predetermined one of the N linked stations to others of the N linked stations,

transmitting the first portion of the data from the predetermined one N linked station to each of the other N linked stations during the assigned first time slot of each cycle period,

transmitting the second portion of the data from the predetermined one N linked station to each of the other N linked stations during the assigned second time slot of each cycle period and before an end of a prescribed time period after transmission of the first portion of the data and the header signal, and

inhibiting by the predetermined one N linked station, after the end of the prescribed time period, further transmission of the second portion of the data to any other N linked station until completion of a current cycle period.

12. The method of claim 11, wherein the step of transmitting the first portion of the data includes the step of transmitting a frame containing no data when there is no data to be transmitted by the predetermined one N linked station when the right to transmit data during the first time slot is assigned to the predetermined one N linked station.

13. The method of claim 11, wherein the step of transmitting the second portion of the data includes the step of transmitting a frame containing no data when there is no data to be transmitted by the predetermined one N linked station when the right to transmit data during the second time slot is assigned to the predetermined one N linked station.

14. The method of claim 11, further including the step performed by the predetermined one N linked station, of receiving a frame containing one of the first and second transmitted data portions;

wherein the steps of transmitting the first portion and the second portion of the data include the step of transmitting a frame containing no data when no frame is received by the predetermined one N linked station for a predetermined time.

15. The method of claim 11, wherein the step of inhibiting further transmission of the second portion of the data includes the step of transmitting a frame containing no data.

16. The method of claim 11, wherein the step of transmitting the second portion of the data includes the step of measuring a prescribed time from a time when the transmission of the first portion of the data is completed.

17. The method of claim 11, wherein the step of transmitting the header signal includes the step of measuring a prescribed time from a time when the header signal is transmitted.

18. A station in a system for transmitting data between N linked stations, where N is greater than 2, one of which is a master station, within a cycle period defined by successive transmissions of a header signal indicating a start of a data transmission by the N linked stations, only one station having a right to transmit data at a given time, the data transmitted by the station including a first portion for which real-time characteristics are required, and a second portion for which real-time characteristics are not required, the station comprising:

transmission means for transmitting a header signal to another station when the station including the transmission means is designated a master station, and for transmitting ones of both the first and second data portions to another station,

receiver means for receiving a header signal and first and second data portions transmitted from another station, and

control means, coupled to the transmission means and the receiver means, for assigning to the station the right to transmit data in the cycle period, wherein the cycle period is divided into 2N time slots such that each of the N linked stations is assigned a data transmission right during first and second time slots during each cycle period, the first portion of data being transmitted only in the first time slot and the second portion being transmitted by the transmission means only in the second time slot, wherein the control means is able to transmit data only in the assigned first and second time slots.

19. A system for transmitting data between N linked stations, where N is greater than 2, one of which is designated a master station, within a cycle period defined as a period between successive transmissions of a header signal indicating a start of data transmission by the N linked stations, only one station having a right to transmit data at a given time, the data transmitted by each station including a first portion for which real-time characteristics are required, and a second portion for which real-time characteristics are not required, each Mth station (1<

=M<

=N) comprising;

transmission means for transmitting a header signal to another station when the station including the transmission means is designated a master station, and for transmitting ones of both the first and second data portions to another station,

receiver means for receiving a header signal and first and second data portions transmitted from another station, and

control means, coupled to the transmission means and the receiver means, for assigning to the station including the control means the right to transmit data in a cycle period, wherein the cycle period is divided into 2N time slots, and wherein data is transmitted by the control means only in a first time slot constituting an Mth time slot, and a second time slot constituting an N+Mth time slot within the cycle period and for transmitting the first portion of the data separate from transmission of the second portion of the data, the first portion being transmitted by the transmission means in the first time slot and the second portion being transmitted by the transmission means in the second time slot, wherein the control means is able to transmit data only in the first and second time slots.