Browse Prior Art Database

Removal of Glitches from Digital Lines Using Circuit Delays

IP.com Disclosure Number: IPCOM000112861D
Original Publication Date: 1994-Jun-01
Included in the Prior Art Database: 2005-Mar-27
Document File: 2 page(s) / 45K

Publishing Venue

IBM

Related People

Jones, CE: AUTHOR

Abstract

A technique for removing glitches from a digital signal is disclosed. Glitches are removed by the application of pulse shrinkers.

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

Removal of Glitches from Digital Lines Using Circuit Delays

      A technique for removing glitches from a digital signal is
disclosed.  Glitches are removed by the application of pulse
shrinkers.

      The invention makes use of the fact that the pulse width of a
glitch is less than the pulse width of a valid signal.  By shrinking
all pulses on the line, only those that are wider than a certain
threshold will pass through (Fig. 1).

      Pulse shrinkers are implemented by ANDing the signal with a
delayed version of the signal (Fig. 2).  This will shrink a
positive-going pulse.  To shrink a negative-going pulse, the signal
is inverted before being fed into the pulse shrinker.

      To handle both negative-going and positive-going glitches, two
pulse shrinkers are used.  Because negative-going pulse shrinkers
expand positive glitches and positive-going pulse shrinkers expand
negative glitches, additional logic is used to control which pulse
shrinker is used at any given time.

      If the signal is low, then the output of the positive-going
pulse shrinker is used to detect the low-to-high signal transition.

      If the signal is high, then the negative-going pulse shrinker
is used to detect the high-to-low signal transition.  A latch is used
to hold the current state of the signal (Fig. 3).