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Time-locking method for stations which form part of a local loop network, and local loop network for performing this time-locking method

  • US 4,535,449 A
  • Filed: 05/02/1983
  • Issued: 08/13/1985
  • Est. Priority Date: 04/30/1982
  • Status: Expired due to Fees
First Claim
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1. In a local loop network comprising a plurality of stations which are distributed along a bus, each station being connected to the bus by way of a coupler, said bus comprising a looping unit inserted in the bus, a method for the time-locking of the stations, said method including an initialization phase for allocating to each station a time reference with respect to a master clock of the looping unit, characterized in that the initialization phase forms part of a transmission phase which comprises the following steps:

  • (a) the transmission of a frame, referred to as the transmission frame, by the looping unit, said transmission frame comprising;

    a synchronization word which initializes the transmission and initialization phase,at least one slot which initially does not contain data and which has for each station a different position with respect to the position of the synchronization word, said position corresponding to the time position occupied by each station in the transmission frame;

    (b) the generating of a transmission command by at least one station after the transmission of the synchronization word;

    (d) the insertion, by the station and under the control of the transmission command, of a word into the empty slot allocated to the station;

    said transmission phase being followed by a receiving phase which comprises the following steps;

    (a) the demodulation of the transmission frame by the looping unit;

    (b) the retransmission, in the form of a frame which is referred to as the receiving frame, of said demodulated transmission frame by the looping unit,(c) the measurement by the station of the delay, with respect to the beginning of the slot allocated thereto, with which the word has been inserted into the allocated slot by the station during the transmission phase;

    (d) the storage by the station of the measured delay value in order to enable the station to advance the insertion of the word into the allocated slot during a next transmission by a period which corresponds to the delay value.

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