Method and apparatus for recovering data and clock information from a self-clocking data stream

In a data transmission system using self-clocking bi-phase coded bit streams, said bit streams having predetermined bit period and two voltage levels with negative-going and positive-going voltage level transitions occurring in the steam to indicate clock information and data information, at least a first such voltage level transition and possibly a second voltage level transition occuring in each bit period, apparatus for recovering said information comprising:

• means for generating from each voltage level transition in the coded bit stream, a pluse having a first polarity,
• a non-retriggerably one-shot to which is applied the pulse of first polarity, siad one-shot producing an output pulse having a duration that is approximately the time interval between said first and second voltage transitions and being non-retriggerable after said pulse terminates for a period of time less than the difference between the duration of a bit period and the duration of said output pulse, said output pulse providing clock information derived from the coded bit stream, wherein said one-shot comprises:
• a first logic gate having at least two inputs, a first of which is connected to said generating means and received said pulse having a first polarity,
• means connected to an output of said first logic gate for generating a ramp signal whose magnitude decreases gradually from a peak value,
• a second logic gate connected to said ramp signal generating means for generating said output pulse while the magnitude of said ramp signal exceeds a threshold logic value, and
• means for feeding said output pulse back to a second input of the first logic gate to inhibit said gate so that the one-shot cannot be retriggered while said output pulse is present at said second input to the first logic gate, and
• bistable storage means having a clock input to which clock information from an output of the one-shot is applied and a data input to which the coded bit stream is applied, said clock information being delayed by less than said time interval relative to any delay experienced by the coded bit stream, said bistable storage means providing at an output thereof data information decoded from the coded bit stream.

In a data transmission system using self-clocking bi-phase coded bit streams, said bit streams having a predetermined bit period and two voltage levels with negative-going and positive-going voltage level transitions occurring in the stream to indicate clock information and data information, at least a first such voltage level transition and possibly a second voltage transition occurring in each bit period, a method for recovering said information comprising the steps of:

• applying the coded bit stream to a data input to a bistable storage means,
• generating from each voltage level transition in the coded bit stream, a pulse having a first polarity,
• applying said pulse to a non-retriggerable one-shot to produce an output pulse having a duration that is approximately the time interval between said first and second voltage transitions, said output pulse providing clock information derived from the coded bit stream,
• inhibiting said one-shot so that it cannot be retriggered after said pulse terminates for a period of time less than the difference between the duration of a bit period and the duration of said output pulse, and
• applying said clock information to a clock input of said bistable storage means to clock said data stream into said bistable storage means, said clock information being delayed by less than said time interval relative to any delay experienced by the coded bit stream, said bistable storage means providing at an output thereof data information decoded from the coded bit stream.

In a data transmission system using self-clocking bi-phase coded bit streams, said bit streams having a predetermined bit period and two voltage levels with negative-going and positive-going voltage level transitions occuring in the stream to indicate clock information and data information, at least a first such voltage level transition and possibly a second voltage transition occurring in each bit period, a method for recovering said information comprising the steps of:

• applying the coded bit stream to a data input to a bistable storage means,
• generating from each voltage level transition in the coded bit stream, a pulse having a first polarity,
• applying said pulse to a non-retriggerably one-shot to produce an output pulse having a duration that is approximately the time interval between said first and second voltage transitions, said output pulse providing clock information derived from the coded bit stream, wherein said one-shot comprises:
• a first logic gate having at least two inputs, a first of which is connected to said generating means and receives said pulse having a first polarity,
• means connected to an output of said first logic gate for generating a ramp signal whose magnitude decreases gradually from a peak value, and
• a second logic gate connected to said ramp signal generating means for generating said output pulse while the magnitude of said ramp signal exceeds a threshold logic value,
• inhibiting said one-shot so that it cannot be retriggered after said pulse terminates for a period of time less than the difference between the duration of a bit period and the duration of said output pulse, said step of inhibiting the one-shot comprising the step of feeding said output pulse back to a second input of the first logic to inhibit said gate so that the one-shot cannot be retriggered while said output pulse is present at said second input to the first logic gate, and
• applying said clock information to a clock input of said bistable storage means to clock said data stream into said bistable storage means, said clock information being delayed by less than said time interval relative to any delay experienced by the coded bit stream, said bistable storage means providing at an output thereof data information decoded from the coded bit stream.