Browse Prior Art Database

Automatic Detection of Oscillator Frequency Drift

IP.com Disclosure Number: IPCOM000110729D
Original Publication Date: 1992-Dec-01
Included in the Prior Art Database: 2005-Mar-25
Document File: 1 page(s) / 38K

Publishing Venue

IBM

Related People

Barrett, WM: AUTHOR [+3]

Abstract

A method to detect frequency drift between two asynchronous oscillators that have the same frequency is disclosed. The sensitivity of the detector is easily changed.

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This is the abbreviated version, containing approximately 100% of the total text.

Automatic Detection of Oscillator Frequency Drift

      A method to detect frequency drift between two asynchronous
oscillators that have the same frequency is disclosed.  The
sensitivity of the detector is easily changed.

      To detect frequency drift between two asynchronous oscillators
with the same frequency, two free-running counters are used.  Each
counter is clocked by a different oscillator.  The initial value of
the first counter is zero.  The initial value of the second is one
half of the maximum value of the counter.  The counters are
periodically reset to their initial values.  The sensitivity of the
detector is determined by the size of the counters and the interval
at which the counters are reset to their initial values.

      An error condition is detected whenever the values of the two
counters become equal.  This will only occur if the two counters have
drifted in relation to each other in one direction or the other by
more than a predetermined amount.  The counters should be designed so
that as they change states the two counters do not glitch through a
state where they are equal.  This can be realized by using gray-code
counters.

      This solution effectively measures the average amount of drift
between the two oscillators over a fixed period of time.

      Disclosed anonymously.