Data Recovery through event based equivalent time sampling
AssigneeCredence Systems Corporation
InventorTad Labrie
Life of this patent
Estimating the term…
Abstract
A system uses an event based equivalent time sampling method for ascertaining a value of each bit of a data frame repeated in a digital signal of indeterminate phase. The system measures time intervals between rising edges of the digital signal and a reference time and between falling edges of the digital and that reference time in response to pulses of a periodic arming signal. The measured time intervals are then normalized to equivalent time intervals and those intervals analyzed to determine values of each bit of the data frame.
Claims30
A method for ascertaining a value of each bit of a data frame of nominal duration PF periodically repeating in a digital signal, wherein each bit occupies a time slot of nominal duration PD within the data frame, wherein the digital signal conveys an alternating sequence of rising and falling edges representing state changes between successive bits of the data frame, the method comprising the steps of:
- a. measuring time intervals of said rising and falling edges relative to a reference time and generating timing data representing said time intervals, and
- b. ascertaining a value of each bit of the data frame from said timing data.
An apparatus for ascertaining a value of each bit of a data frame of nominal duration PF periodically repeating in a digital signal, wherein each bit occupies a time slot of nominal duration PD within the data frame, wherein the digital signal conveys an alternating sequence of rising and falling edges representing state changes between successive bits of the data frame, the apparatus comprising:
- first means for measuring time intervals of said rising and falling edges relative to a reference time and generating timing data representing said time intervals, and
- second means for ascertaining a value of each bit of the data frame from said timing data.
An apparatus for determining whether a digital signal has excessive jitter, wherein the digital signal conveys a periodically repeating data frame of nominal duration PF, the data frame containing a first sequence of data bits, wherein each data bit occupies a time slot of nominal duration PD within the data frame, wherein the digital signal conveys an alternating sequence of rising and falling edges representing state changes between successive bits of the digital signal, the apparatus comprising:
- first means for measuring time intervals of said rising and falling edges relative to a reference time and generating timing data representing said time intervals,
- second means for determining from said timing data a second sequence of data bits apparently contained in each data frame, and
- third means for comparing the first sequence to the second sequence to determine whether the digital signal has excessive jitter.
A method for determining whether a digital signal has excessive jitter, wherein the digital signal nominally contains a periodically repeating data frame of nominal duration PF, the data frame containing a first sequence of data bits, wherein each data bit occupies a time slot of nominal duration PD within the data frame, wherein the digital signal conveys an alternating sequence of rising and falling edges representing state changes between successive bits of the digital signal, the method comprising the steps of:
- a. measuring time intervals of said rising and falling edges relative to a reference time and generating timing data representing said time intervals,
- b. determining from said timing data a second sequence of data bits apparently contained in each data frame, and
- c. comparing the first sequence to the second sequence to determine whether the digital signal has excessive jitter.
Dependencies are inferred from the claim text.