US3633166A - Data transmission method and serial loop data transmission system - Google Patents

Data transmission method and serial loop data transmission system Download PDF

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Publication number
US3633166A
US3633166A US34781A US3633166DA US3633166A US 3633166 A US3633166 A US 3633166A US 34781 A US34781 A US 34781A US 3633166D A US3633166D A US 3633166DA US 3633166 A US3633166 A US 3633166A
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Prior art keywords
station
bit configuration
loop
central
remote
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US34781A
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English (en)
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Jean L Picard
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International Business Machines Corp
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International Business Machines Corp
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    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L12/00—Data switching networks
    • H04L12/28—Data switching networks characterised by path configuration, e.g. LAN [Local Area Networks] or WAN [Wide Area Networks]
    • H04L12/42—Loop networks
    • H04L12/423—Loop networks with centralised control, e.g. polling

Definitions

  • the central unit then sends a sequence of A US. Cl 340/163, characters which are intercepted by the terminals which have 340/147 their switch in the second position and which shift the identifi- Iut.
  • This invention relates to a method for transmitting data between atransmission control unit'and a plurality of serially connected terminals arranged in closed loop.
  • the central office is generally provided with one or more computers, which will be called hereinafter transmission control unit," having a very large capacity disk or tape units for memorizing all the incoming information.
  • the transmission control unit communicates with the branches through telephone cables, by means of modulator-demodulator systems, or modems, whichare well-known in the art.
  • a terminal which operates the various incoming transaction machines, transmits the information over the same telephone lines via the modems.
  • the terminals are radially connected to the transmission control unit. This is the so-called point-topoint configuration.
  • Such a system requires one modem per line at the transmission control unit and one modem per terminal. The cost of all these modems is a high percentage of the total cost of the installation. 7
  • Another well-known system the so-called multiple terminals" configuration, consists in connecting in parallel all the terminals on a single line. This reduces the total number of the modems used since only one modem is required at the transmission control unit. Such a system is wasteful of transmission capacity since it must start its modulator before it can start transmission.
  • a third well-known system the so-called loop configuration can be used.
  • the terminals are connected in series by a single line coming from and leading back to the transmission control unit.
  • the line reaches each terminal through the demodulator of a modern and leaves it through the modulator of the same modem.
  • the information sent over the loop goes through each of the modems. Said modems, therefore, are always in operation. This avoids the loss of time mentioned previously with regard to the multiple terminals" configuration.
  • a prior art method sends a plurality of predetermined instruction characters over the loop from the transmission control unit, which enables the first rank terminal on the line which wants to transmit a message to the transmission control unit, to get ready for a transmission operation and which controls the switching off of the other terminals. Once this terminalhas transmitted its message; it
  • one object of the invention is to provide a data transmission method between a transmission controlunit and a plurality of terminals, wherein the transmission controlunit reassumes control of transmission after each terminal has completed a single transmission.
  • Another object of the invention is to provide a-data transmission method between a transmission control unit and aplurality of terminals, wherein the control unit can request apri-. ority transmission of any terminal over the others.
  • each terminal includes a register and a twoposition switch, the first position short circuiting the tenninal, the second one inserting the register into the loop'.
  • the switch When there is no information from or to the transmission control unit, the switch is in its first position and the transmission control unit is continuously sending characters of a first configuration over the loop.
  • the transmissioncontrol.unit wants to know which terminals are in a condition to transmit information to it, said unit sends a character of a second configuration which is received by each terminal.
  • the terminals which have information to be transmitted to the transmission control unit then, switch their switches into their second positions and transfer their identification code or character to their registers, respectively. Then, the transmission control unit continuously sends first configuration characters over the loop.
  • the terminal identification characters are thus transferred from one register to the next one onto the tra'nsmissioncontrol unit, the terminal switches being respectively switched into their first positions when the first character of the first configuration. is received in the corresponding register. It should be :noted that after the second configuration character, the transmission control unit can continuously send characters of a third con.- figuration, said characters being used only for the transfer of the identification numbers from one register to the next one. Therefore, the transmission control unit receives the series of the identification character of all the terminals which want to transmit information to the control unit, which enables said unit to start data transmission of the different terminals according to a transmission order chosen by it while reassuining control of the transmission of data after each terminal completes transmission.
  • FIG. 4 is a simplifieddia'gram of a terminal for communication on the loop according to another embodiment of the invention.
  • FIG. 5 is a table showing the characters received and transmitted by the terminals on the loop according to the preferred embodiment shown in FIG. 4.
  • FIG. 6 is a simplified diagram of a terminal for communication on the loop according to another embodiment of the invention.
  • FIG. 7 is a table showing the characters received and transmitted by the terminals on the loop according to the preferred embodiment shown in FIG. 6.
  • FIG. 1 is the general arrangement of a data transmission system in a closed circuit, the so-called loop configuration.
  • the transmission control unit 2, or TCU sends data over the closed circuit 4 via a modulator.
  • Said modulator is part of the modulator-demodulator system, or modern.
  • the TCU receives the data from the circuit via the demodulator of modern 3.
  • a plurality of terminals A, B, C can be arranged in the closed circuit. For instance, if reference is made to terminal A, it can be observed that the data sent from the TCU 2 passes through the demodulator of modem 11 ad are then received in the control unit 12.
  • Said control unit can operate on its own a plurality of input-output stations l3, l4, l5, generally placed at the same geographical location. Said stations which include the devices for the introduction of the operated transactions are not part of the invention, and therefore, they will not be described here.
  • the above used term transmission control unit may designate any device provided with a memory and a control unit capable of handling data transmission and data reception, such as a computer provided with adequate peripheral units, a communication controlling device or a line concentrator.
  • FIG. 2 shows a terminal in a schematic form.
  • the main units for the embodiment of the invention are a shift register the capacity of which corresponds to the format of the characters used during the transmission wherein the data are received or transmitted bit after bit over the loop and a switch 24 with two positions and 26. Position 25 is used to short circuit the terminal and position 26 causes the data to pass through register 20. While switch 24 has been shown in a simplified manner, it is obvious because of the rate of the data flow that it will include electronic circuits which are well known in the art.
  • the transmission control unit sends continuously characters of configuration A over the loop. If, for instance, the data transmission is made according to the synchronous mode, these characters are synchronization characters which cause the terminals to get synchronized with the TCU. As long as the A configuration characters are being received by the terminal, switch 24 is in position 25.
  • the TCU When the TCU wants to know which terminals desire to transmit information to it, it then sends a character of a second configuration B.
  • This B configuration character is sent all along the loop since the terminal switches are in positions 25, respectively. But this character is also loaded bit after bit in the shift register of each terminal.
  • the device 23 controls two operations, namely the parallel transfer of the identification number of the terminal from a memory 22 to register 20 on the one hand and the switching of switch 20 which switches from position 25 to position 26 on the other hand. If transmission is not required, switch 24 is maintained in position 25.
  • decoding and control operations are achieved within a very short time period with respect to the time duration of a bit. Since the sampling of the bits is made at about the midtime of the time period of a bit, there is enough time left after the sampling of the last bit in the character to complete all these decoding and control operations.
  • the transmission control unit After the transmission control unit has sent the B configuration character, it resumes sending the A configuration characters.
  • the transmission control unit could send characters having another configuration over the loop without modifying in any way the rest of the procedure. Since the terminals which had no information to be transmitted to the TCU have maintained their switches in positions 25, respectively, they are of no interest in the following description since they are short circuited.
  • the first terminal which has its switch 24 in position 26 receives the first A configuration character transmitted by the TCU. As this character is being loaded into shift register 20, the identification character is transmitted bit after bit over the loop through line 27 due to switch 24 being in position 26. In the meantime, the bits of the identification character of this first terminal are loaded in the shift register of the second terminal having its switch in position 26 (or in other words, having information to be transmitted). Likewise, as the bits are arriving, the identification character of this second terminal is transmitted over the loop and so on. Therefore, there is a step-by-step shift and the transmission control unit receives the identification character of the last terminal of the loop that desires to transmit information.
  • the transmission control unit When the transmission control unit sends the second character of configuration A, it is received by the second terminal which desires to transmit information.
  • the shift of the identification characters occurs in like manner as seen previously, and the transmission control unit therefore receives the identification character of the next to last terminal on the loop that desires to transmit information.
  • the terminal which received it switches its switch back to position 25, thus causing the next A configuration character to reach directly the next terminal which has its switch in position 26.
  • each terminal will be provided with a buffer memory containing the different characters of the identification code before transmitting them via register 20.
  • the transmission control unit receives consecutively, all the identification characters of the terminals having information to be transmitted according to an order which is opposite to their respective geographical positions on the loop. Said unit sends A configuration characters until it receives an A configuration character which is immediately following the last identification character corresponding to the geographically first terminal having information to be transmitted. The reception of this character indicates to the transmission control unit that it has received all the identification characters of the terminals desiring to transmit information. At this time, the TCU may ask any one of said terminals to transmit its information. Contrary to the prior art devices, the first terminal on the loop will not necessarily be the first to transmit its information.
  • the information control unit has only to send a C configuration character followed by the identification number of the selected terminal. The addressed terminal will cause switch 24 to move to position 26. Then the terminal will load the shift register 20 with the information characters coming from memory 22. The continuous sending of A configuration characters will cause register 20 to send said characters over the loop bit after bit.
  • FIG. 3 For a better understanding of the preferred embodiment of the invention, reference is made to FIG. 3.
  • the transmission control unit namely terminals l, 3, 5 having identification numbers No. 1, No. 2, No. 3, respectively. It is obvious that these numbers are given only for a descriptive purpose and that, in fact, a number is represented by a single character of a specific configuration (or by a group of several characters as mentioned previously).
  • the first column indicates the succession of the characters transmitted from the TCU and the last column, the succession of the characters received by the TCU.
  • the contents of the register at the end of the reception of a character are indicated on the one hand, and the position of switch 24v at the end of the reception of this very character is on the other hand. It can be observed, as seen previously, that the TCU receives first the B configuration character, then the succession of the identification numbers of the terminals having information to be transmitted according to an order opposite to their respective geographical positions on the loop, the A configuration characters which indicate that the TCU has duly received all the identification numbers of the terminals having information to be transmitted.
  • register receives the characters coming from the transmission control unit, however, it is register 38 which is loaded from memory 32 with the characters that the terminal is transmitting to the TCU.
  • the transmission control unit sends one B configuration character in order to ascertain which terminals have information to be transmitted.
  • the B configuration character is received in register 30, is decoded by decoding device 31 and'should the terminal have information to be transmitted, the control device 33 which receives the decoding information from device 31, controls the parallel transfer of the identification number of the terminal from memory 32 to register 38 at the end of the reception of the B configuration character in register 30. In the same time, the device 33 controls the change in position of the switch 34 which passes from position 35 to position 37. Thus, all the terminals having information to be transmitted to the TCU have their switches in positions 37 and have loaded register 38 with their identification character, respectively. After sending the B configuration character, the transmission control unit resumes sending A configuration characters. If the first terminal on the loop ready to transmit information is considered, it will receive an A configuration character.
  • the terminal proceeds to the sending of its identification number bit after bit from register 38 via position 37 of switch 34. Once the transmission of the identification number is over, the terminal switches its switch to position 35.
  • the second terminal having information to be transmitted receives the identification number of the previous terminal in its register 30 as it is transmitting its identification number from register 38. But because this terminal does not receive any A configuration character from its register 30, its switches its switch 34 to position 36. The same holds true for each of the following terminals having information to be transmitted which switch their switches 34 to positions 36, respectively.
  • the preferred embodiment of the invention is considered anew with a two-position switch.
  • the example shown in the table of FIG. 5 is used for a better understanding of the above explained embodiment.
  • the terminals 1 and 3 have information to be transmitted from amongst the three terminals on the loop.
  • the transmission control unit receives the identification numbers of the terminals according to an order opposite to their geographical positions on the loop.
  • the transmission is carried out in the start-stop mode, it is the detection of the first bit in the character, i.e., the bit start received in register 30 by device 31, that will enable device 33 to control the beginning of the transmission, bit after bit, of the identification number contained in register 38; Whereas in the synchronousmode wherein the characters are occupying consecutive time intervals, the transmission of the identification number contained in register 38is made without taking the bits received in register30 into account.
  • the TCU Once the TCU has'all the identification numbersof'the te'rminals having information to be transmitted, it sends a C configuration character followed by the identification number of the terminal which is asked to transmit its information. But in this embodiment, the designated terminal switches its switch to position 37 in order to send the information characters from register 38.
  • the shift register is directly on the loop and the characters coming from the transmission control unit are transferred from one register to the next one without being able to short circuit the terminals as seen in the previous example.
  • the TCU sends a B configuration character
  • this character is received by the register of the first terminal on the loop.
  • the decoding operation of the character by decoder 41 entails no operation.
  • the decoding of the B configuration character will cause the control device 43 to prepare for the transfer of the identification number of the terminal from memory 42 to register 40.
  • the identification character is merely pending and it is only when the following A configuration character sent by the TCU is loaded in register 40 that the identification character is actually transferred in parallel into the register 40.
  • the B configuration character is transferred into the register of the next following terminal.
  • a terminal When a terminal has information to be transmitted, it prepares its identification character in order to transfer it into its register 40 when the first received A configuration character is decoded by decoder 41. But, in fact, said second terminal will receive first the identification character of the first terminal and it will proceed to no operation. The first terminal identification character will be transferred and only after decoding the following A configuration character which immediately follows the identification character of the first terminal will the second terminal identification character be inserted.
  • the sequence of the identification numbers received by the transmission control unit will correspond to the order of the terminals on the loop.
  • the first column indicates the character sent by the TCU and the columns corresponding to the terminals indicate the character which is in the terminal register after the character has been sent by the TCU.
  • the last column indicates the character received by the TCU after the same has transmitted a character.
  • the transmission control unit wanted to know which are the terminals that have information to be transmitted to it. It is obvious for the man skilled in the art that the invention applies also to the case when the transmission control unit has to transmit information to the terminals and must know which are the ones of said terminals that are susceptible to receive information.
  • a method for establishing communications between a central station and a plurality of remote stations connected in a serial loop with said central station comprising the steps of:
  • each said remote station monitoring the bit configuration on the loop for detecting the presence of said second predetermined bit configuration
  • a method for establishing communications between a central station and a plurality of remote stations connected in a serial loop with said central station comprising the steps of:
  • output means at each remote station for transmitting data bits to the next succeeding station
  • switch means for alternatively connecting the shift register to the output means in one state and the input means directly to the output means in its other state
  • decoder means responsive to the contents of said shift register for detecting the said first and second bit configuration and providing outputs indicative thereof;
  • control means responsive to the output indicative of the detection of the second bit configuration for causing said switch means to assume its said other state and for inserting a unique station identification code in the said shift register over the previously received said second bit configuration and for causing said switch means to assume its said first state when the output from the decoder means indicates the reception of the said first bit configuration whereby said central station receives from the output means of the last remote station on the loop a plurality of unique bit configurations each identifying one remote station which has data to send to the central and requires service which may be initiated by the central in any appropriate order since the central is advised of all the remote stations requiring service.
  • a method for establishing communications between a central station and a plurality of remote stations connected in a serial loop with said central station comprising the steps of:
  • each said remote station buffering a predetermined number of incoming bits from the loop before passing the buffered bits onto the next station on the loop;

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  • Engineering & Computer Science (AREA)
  • Computer Networks & Wireless Communication (AREA)
  • Signal Processing (AREA)
  • Small-Scale Networks (AREA)
  • Communication Control (AREA)
  • Computer And Data Communications (AREA)
US34781A 1969-05-16 1970-05-05 Data transmission method and serial loop data transmission system Expired - Lifetime US3633166A (en)

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FR696915337A FR2044650B1 (en, 2012) 1969-05-16 1969-05-16

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JP (1) JPS5026243B1 (en, 2012)
BE (1) BE749291A (en, 2012)
DE (1) DE2022096C3 (en, 2012)
FI (1) FI53519C (en, 2012)
FR (1) FR2044650B1 (en, 2012)
GB (1) GB1244297A (en, 2012)
NO (1) NO133735C (en, 2012)
SE (1) SE365629B (en, 2012)

Cited By (22)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3752932A (en) * 1971-12-14 1973-08-14 Ibm Loop communications system
US4009469A (en) * 1975-12-19 1977-02-22 Ibm Corporation Loop communications system with method and apparatus for switch to secondary loop
US4051328A (en) * 1974-08-08 1977-09-27 Siemens Aktiengesellschaft Method for operating a digital time division multiplex communication network
US4213182A (en) * 1978-12-06 1980-07-15 General Electric Company Programmable energy load controller system and methods
US4366479A (en) * 1980-02-08 1982-12-28 Hitachi, Ltd. Control information communication method and system through a common signal transmission line
US4456790A (en) * 1982-02-08 1984-06-26 Bell Telephone Laboratories, Incorporated Automated hardware inventory system
US4498167A (en) * 1982-03-01 1985-02-05 International Telephone And Telegraph Corporation TDM Communication system
US4511895A (en) * 1979-10-30 1985-04-16 General Electric Company Method and apparatus for controlling distributed electrical loads
US4517644A (en) * 1980-09-03 1985-05-14 Hitachi, Ltd. Symmetry type loop communication system
US4554659A (en) * 1983-12-12 1985-11-19 At&T Bell Laboratories Data communication network
WO1987007797A1 (en) * 1986-06-09 1987-12-17 Christian Rovsing A/S Af 1984 A method of coupling a data transmitter unit to a signal line and an apparatus for performing the invention
US5113391A (en) * 1990-07-20 1992-05-12 Integrated Network Corporation Intelligent channel unit
US5117225A (en) * 1989-05-01 1992-05-26 Summit Micro Design Computer display screen monitoring system
US5512846A (en) * 1993-09-06 1996-04-30 Mitsubishi Denki Kabushiki Kaisha Signal selecting device controlled by a serially transmitted mode signal requiring but one terminal
US5638334A (en) * 1990-04-18 1997-06-10 Rambus Inc. Integrated circuit I/O using a high performance bus interface
US5754596A (en) * 1994-02-23 1998-05-19 Rosemount Inc. Field transmitter for storing information
US5991841A (en) * 1997-09-24 1999-11-23 Intel Corporation Memory transactions on a low pin count bus
US6047063A (en) * 1996-01-23 2000-04-04 Antec Corporation Methods and apparatus for providing an auxiliary communication line
US6119189A (en) * 1997-09-24 2000-09-12 Intel Corporation Bus master transactions on a low pin count bus
US6131127A (en) * 1997-09-24 2000-10-10 Intel Corporation I/O transactions on a low pin count bus
US6157970A (en) * 1997-09-24 2000-12-05 Intel Corporation Direct memory access system using time-multiplexing for transferring address, data, and control and a separate control line for serially transmitting encoded DMA channel number
US7209997B2 (en) 1990-04-18 2007-04-24 Rambus Inc. Controller device and method for operating same

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US3706974A (en) * 1971-10-27 1972-12-19 Ibm Interface multiplexer
FR2200708B1 (en, 2012) * 1972-09-26 1976-05-07 Ibm
DE2333137C3 (de) * 1973-06-29 1982-11-18 Licentia Patent-Verwaltungs-Gmbh, 6000 Frankfurt Zyklisches Abrufverfahren in einem Datenübertragungssystem
DE3328834A1 (de) * 1983-08-10 1985-02-28 Licentia Patent-Verwaltungs-Gmbh, 6000 Frankfurt Datenuebertragungsssystem mit einer ringfoermigen uebertragungsleitung
DE3424866C2 (de) * 1984-07-06 1986-04-30 Messerschmitt-Bölkow-Blohm GmbH, 8012 Ottobrunn Verfahren und Anordnung zur Übertragung von Daten, insbesondere in einem Flugzeug

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US3444520A (en) * 1965-07-06 1969-05-13 Mobil Oil Corp Control interface for computer controlled supervisory system

Patent Citations (1)

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US3444520A (en) * 1965-07-06 1969-05-13 Mobil Oil Corp Control interface for computer controlled supervisory system

Cited By (30)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3752932A (en) * 1971-12-14 1973-08-14 Ibm Loop communications system
US4051328A (en) * 1974-08-08 1977-09-27 Siemens Aktiengesellschaft Method for operating a digital time division multiplex communication network
US4009469A (en) * 1975-12-19 1977-02-22 Ibm Corporation Loop communications system with method and apparatus for switch to secondary loop
US4213182A (en) * 1978-12-06 1980-07-15 General Electric Company Programmable energy load controller system and methods
US4511895A (en) * 1979-10-30 1985-04-16 General Electric Company Method and apparatus for controlling distributed electrical loads
US4366479A (en) * 1980-02-08 1982-12-28 Hitachi, Ltd. Control information communication method and system through a common signal transmission line
US4517644A (en) * 1980-09-03 1985-05-14 Hitachi, Ltd. Symmetry type loop communication system
US4456790A (en) * 1982-02-08 1984-06-26 Bell Telephone Laboratories, Incorporated Automated hardware inventory system
US4498167A (en) * 1982-03-01 1985-02-05 International Telephone And Telegraph Corporation TDM Communication system
US4554659A (en) * 1983-12-12 1985-11-19 At&T Bell Laboratories Data communication network
WO1987007797A1 (en) * 1986-06-09 1987-12-17 Christian Rovsing A/S Af 1984 A method of coupling a data transmitter unit to a signal line and an apparatus for performing the invention
US5117225A (en) * 1989-05-01 1992-05-26 Summit Micro Design Computer display screen monitoring system
US5638334A (en) * 1990-04-18 1997-06-10 Rambus Inc. Integrated circuit I/O using a high performance bus interface
US5983320A (en) * 1990-04-18 1999-11-09 Rambus, Inc. Method and apparatus for externally configuring and modifying the transaction request response characteristics of a semiconductor device coupled to a bus
US7209997B2 (en) 1990-04-18 2007-04-24 Rambus Inc. Controller device and method for operating same
US20050141332A1 (en) * 1990-04-18 2005-06-30 Rambus Inc. Semiconductor device including a register to store a value that is representative of device type information
US5809263A (en) * 1990-04-18 1998-09-15 Rambus Inc. Integrated circuit I/O using a high performance bus interface
US5841580A (en) * 1990-04-18 1998-11-24 Rambus, Inc. Integrated circuit I/O using a high performance bus interface
US5915105A (en) * 1990-04-18 1999-06-22 Rambus Inc. Integrated circuit I/O using a high performance bus interface
US5928343A (en) * 1990-04-18 1999-07-27 Rambus Inc. Memory module having memory devices containing internal device ID registers and method of initializing same
US5954804A (en) * 1990-04-18 1999-09-21 Rambus Inc. Synchronous memory device having an internal register
US20040114454A1 (en) * 1990-04-18 2004-06-17 Rambus Inc. Memory device and method for operating same
US5113391A (en) * 1990-07-20 1992-05-12 Integrated Network Corporation Intelligent channel unit
US5512846A (en) * 1993-09-06 1996-04-30 Mitsubishi Denki Kabushiki Kaisha Signal selecting device controlled by a serially transmitted mode signal requiring but one terminal
US5754596A (en) * 1994-02-23 1998-05-19 Rosemount Inc. Field transmitter for storing information
US6047063A (en) * 1996-01-23 2000-04-04 Antec Corporation Methods and apparatus for providing an auxiliary communication line
US5991841A (en) * 1997-09-24 1999-11-23 Intel Corporation Memory transactions on a low pin count bus
US6119189A (en) * 1997-09-24 2000-09-12 Intel Corporation Bus master transactions on a low pin count bus
US6131127A (en) * 1997-09-24 2000-10-10 Intel Corporation I/O transactions on a low pin count bus
US6157970A (en) * 1997-09-24 2000-12-05 Intel Corporation Direct memory access system using time-multiplexing for transferring address, data, and control and a separate control line for serially transmitting encoded DMA channel number

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Publication number Publication date
BE749291A (fr) 1970-10-01
NO133735C (en, 2012) 1976-06-16
GB1244297A (en) 1971-08-25
JPS5026243B1 (en, 2012) 1975-08-29
FI53519C (fi) 1978-05-10
FR2044650A1 (en, 2012) 1971-02-26
SE365629B (en, 2012) 1974-03-25
DE2022096A1 (de) 1970-11-19
DE2022096B2 (de) 1974-07-18
FI53519B (en, 2012) 1978-01-31
FR2044650B1 (en, 2012) 1974-06-14
NO133735B (en, 2012) 1976-03-08
DE2022096C3 (de) 1975-03-20

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