Apparatus and method for skew measurement
AssigneeNational Semiconductor Corporation
InventorsVaradarajan Devnath, Vijaya Ceekala, James B. Wieser, Lawrence K. Whitcomb
Life of this patent
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Abstract
A skew measurement system and method wherein each of the signals among which the skew is to be determined is connected one at a time to a clock recovery loop. The locked state of the clock recovery loop is used as an indicator of the skew of the data signal relative to the internal clock of the clock recovery loop. By measuring the difference between the locked state of different signals, their relative skew can be measured.
Claims20
A method for skew measurement, comprising:
- receiving a first data signal;
- determining a first value corresponding to a phase offset of the first data signal;
- receiving a second data signal;
- determining a second value corresponding to a phase offset of the second data signal;
- calculating a skew measurement from the first value and the second value;
- and
- comparing the first data signal to a plurality of signals, each of the plurality of signals having a different phase offset and an associated control word value.
A method for skew measurement, comprising:
- receiving a first data signal;
- determining a first value corresponding to a phase offset of the first data signal;
- receiving a second data signal;
- determining a second value corresponding to a phase offset of the second data signal;
- calculating a skew measurement from the first value and the second value;
- and
- generating a plurality of reference signals, each reference signal having a different phase offset.
A skew measurement system, comprising:
- means for receiving a first data signal;
- means for determining a first value corresponding to a phase offset of the first data signal;
- means for receiving a second data signal;
- means for determining a second value corresponding to a phase offset of the second data signal;
- and
- means for calculating a skew measurement from the first value and the second value;
- and
- means for comparing the first data signal to a plurality of signals, each of the plurality of signals having a different phase offset and an associated control word value.
A skew measurement system, comprising:
- means for receiving a first data signal;
- means for determining a first value corresponding to a phase offset of the first data signal;
- means for receiving a second data signal;
- means for determining a second value corresponding to a phase offset of the second data signal;
- and
- means for calculating a skew measurement from the first value and the second value;
- and
- means for generating a plurality of reference signals, each reference signal having a different phase offset.
A skew measurement system, comprising:
- a clock phase generator configured to receive a control word input and to generate an output clock signal with a phase offset the control word;
- a phase detector configured to compare the output clock signal with an input data signal and to generate a comparison output;
- an adaptation block configured to generate the control word according to the comparison output,
- wherein when the comparison signal indicates that the output clock signal corresponds to the input data signal, a value corresponding to the control word is stored.
Dependencies are inferred from the claim text.