Fully digital data separator and frequency multiplier
First Claim
1. A digital data separator for receiving a data input signal over a serial data in (SDI) line and delivering a clock signal output, said digital data separator comprising:
- an early and late logic unit, said early and late logic unit comprising;
a phase shift accumulator (PSA) register having an input, said PSA register being actuated via said input so as to change a binary value stored in said PSA register when a phase difference exists between said data input signal and said clock signal output, anda limit detector connected to said PSA register, said limit detector delivering an output when the binary value stored in said PSA register reaches a predetermined limit;
a bit length register (BLR) logic unit, said BLR logic unit comprising a counter register, said counter register counting at a fast clock rate, said output from said limit detector controlling the magnitude of a binary value to be loaded into said counter register; and
a counter oscillator, said counter oscillator receiving a signal from said BLR logic unit when said counter register reaches a selected binary value, said counter oscillator delivering said clock signal output in response to said signal from said BLR logic unit.
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Abstract
The data separator of this invention may be used for extracting clock and data signals from a serial stream of bits read from a magnetic disk or tape. The data separator is supplied with a "fast" clock pulse generated by a frequency multiplexer. After a lock indication from the frequency multiplier, during the first eight serial data pulses the frequency and phase of the data separator are synchronized to the serial data pulses. Then an early and late logic unit keeps track digitally of the cumulative phase difference between the incoming data stream and the output of the data separator. When the cumulative phase difference reaches predetermined limits, the phase of the output is adjusted. If a second phase adjustment is required in the same direction (i.e., early or late), the frequency of the output is adjusted. The output of the data separator is generated by a decrementing register, the phase or frequency of the data separator being adjusted by increasing or decreasing the initial value loaded into the decrementing register. The data separator is fully digital.
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Citations
42 Claims
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1. A digital data separator for receiving a data input signal over a serial data in (SDI) line and delivering a clock signal output, said digital data separator comprising:
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an early and late logic unit, said early and late logic unit comprising; a phase shift accumulator (PSA) register having an input, said PSA register being actuated via said input so as to change a binary value stored in said PSA register when a phase difference exists between said data input signal and said clock signal output, and a limit detector connected to said PSA register, said limit detector delivering an output when the binary value stored in said PSA register reaches a predetermined limit; a bit length register (BLR) logic unit, said BLR logic unit comprising a counter register, said counter register counting at a fast clock rate, said output from said limit detector controlling the magnitude of a binary value to be loaded into said counter register; and a counter oscillator, said counter oscillator receiving a signal from said BLR logic unit when said counter register reaches a selected binary value, said counter oscillator delivering said clock signal output in response to said signal from said BLR logic unit. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20)
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21. A digital data separator for receiving serial input data originating in a recording medium and generating in response to said serial input data a digital output signal, said digital data separator comprising:
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an early and late logic unit, said early and late logic unit comprising a first register which records a cumulative phase difference between said serial input data and said digital output signal and generates an output when said cumulative phase difference reaches a predetermined level; a bit length logic unit, said bit length logic unit comprising a second register, said second register cycling between a first binary value and a second binary value, said first binary value being variable, said output from said early and late logic unit controlling the magnitude of said first binary value thereby to control the time required for said second register to count from said first binary value to said second binary value; and a counter oscillator, said counter oscillator receiving a bit detect signal when said second register reaches a predetermined binary value and responsively providing said digital output signal. - View Dependent Claims (22, 23, 24, 25, 26, 27, 28, 29)
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30. A method of converting a serial data input to a digital output signal, said method comprising the steps of:
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(a) digitally recording a cumulative phase difference between said serial data input and said digital output signal, said step (a) comprising.; providing a first register; causing said first register to count at a fast clock rate in a first direction when a pulse of said serial data input occurs before a selected point in a bit cell of said digital output signal; and causing said first register to count at said fast clock rate in a second direction when a pulse of said serial data input occurs after said selected point in said bit cell of said digital output signal; (b) detecting when said cumulative phase difference reaches a predetermined limit; and (c) altering the phase and/or frequency of said digital output signal when said cumulative phase difference reaches said predetermined limit. - View Dependent Claims (31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42)
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Specification