Ring bus station having dual oscillators

In a transmit-receive station, with a local user, adapted for connection to a high speed digital data ring bus:

• a transmitter connected to relay data received on said ring bus and send data information originating at said transmit-receive station;
• a receiver capable of simultaneously transferring data received on said ring bus to the local user and to said transmitter;
• means for generating a first clocking signal having its frequency and phase controlled by the received data;
• a local crystal controlled oscillator having a frequency essentially equal to the frequency of the received data but at an indeterminate phase for generating a second clocking signal;
• means for connecting the first clocking signal to control operation of said receiver;
• and
• switching means connected to control the frequency and phase of signals outputted from said transmitter (1) from one of said clocking signals when relaying received data and (2) from the other of said clocking signals when sending data information on said ring bus which originates at said transmit-receive station.

A dynamic loop system for controlling transmission of data bit signals on a ring bus for transmission of data among a plural number of stations wherein each station has first and second oscillators, the first being used for re-transmission of loop data bit signals that originate at another station and a second being used for transmission of loop data bit signals originating at said station, said system comprising;

• means for controlling the frequency and phase of the first oscillator that receives loop data bit signals arriving at said station and to produce an output clocking signal in a controlled phase relative to said arriving data bit signals;
• a phase selector circuit connected to provide output clocking signals from said second oscillator at a plurality of phases;
• a phase comparison circuit connected to receive output signals from said first oscillator and from said phase selector circuit to produce a control signal;
• and
• means connecting the control signal to an input of said phase selector circuit for connecting the phase of the output signal from said second oscillator used for controlling frequency and phase of transmission of data bit signals to reduce misalignment between the phase of signals controlling transmission of the start of a new originating signal and the phase of prior received data bit signals.

In a ring bus transmission system having a plurality of stations each connected to alternately be "closed" to relay or be "open" to originate messages in a phase encoded Manchester signal that circulates around said ring bus, said system comprising at each station:

• a first local oscillator and a second local oscillator;
• a receiver for receiving signals on said ring bus;
• a transmitter for sending signals on said ring bus, said transmitter being controlled by a clock signal from one of said first or second local oscillators;
• means for controlling the first local oscillator frequency and phase of each station to constantly produce a clock signal which maintains sync with the received data bits and for controlling re-transmission when the station is "closed";
• means whereby the transmitter is controlled when the station is "open" by a clock signal from said second local oscillator;
• and
• means for varying the output phase of the second local oscillator to phase track the phase of the clock signal from the first oscillator when the station is in a "closed" condition so that upon converting to an "open" condition to originate a transmission of a data message, the new clock signal has a phase such that the shift from the phase of the first oscillator clock signal is minimized.

In a ring bus system wherein each station is capable of transmitting to and receiving from other stations connected thereto on an asynchronous basis controlled by a token that is circulated around the ring bus following transmission of each data message frame:

• a first clock means responsive to an incoming pulse train at the station on the ring bus for generating clocking signals for controlling the frequency and phase of a station transmitter for relaying on the ring bus data messages originating at another station connected to said ring bus;
• a second crystal controlled clock means at the station that is connected to the station transmitter to control the frequency and phase of said station transmitter for transmitting data message frames originating at said station and a token issued thereafter, said token having a status indicating the ring bus is available;
• a token buffer register at said station for receiving the issued token after the token has circulated around the ring bus;
• and
• means at said station connected to the token buffer register for repeatedly re-issuing the token using a clock signal from said second clock means for so long as the token still has a status indicating the ring bus remains available;
• and
• means effective, when the received token indicates that a new data message has originated at another station, for substituting a clock signal from said first clock means for the clock signal used for re-issuing the token.