Terminal access protocol circuit for optical fiber star network

Claim 1

In each of a plurality of terminals interconnected by an optical fiber star network for serial exchanges of information among said terminals through a star center, an access protocol circuit comprising: a random access memory for buffering received information comprising queue state data from all said terminals; processing means responsive to the buffered queue state data for determining when said each terminal can transmit information through said star center without interfering with the transmission of information from any other of said terminals; a read only memory for storing the physical addresses of all said terminals; measuring means responsive to said processing means for measuring the distance from the star center to said each terminal, said measuring means comprising: driver message means comprising an oscillator for transmitting a driver message to said star center and for receiving a corresponding echo therefrom and for generating a regular sequence of clock pulses; means for activating said driver message means in a predetermined time sequence relative to the activation of the driver means in the other terminals of said network, in accordance with the physical terminal addresses stored in said ROM, the driver means in the terminal nearest to the network star center being the first to be so activated; delay counting means for counting said clock pulses from the time said driver message means is activated until the time said echo signal is received to thereby generate a delay count corresponding to the distance from the terminal to the star center, and means for storing said delay count; output register means for storing a queue state data word output from said processing means; transmission delay counting means responsive to the stored delay count for generating a start-of-transmission pulse at a time when the terminal should commence transmitting information so that it will arrive at said star center at the time determined by said processing means; and transmission means for transmitting the queue state data stored in said output register means in response to an end of count pulse from said transmission delay counting means.