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Digital Oscillator Adjusted by the Reference Clock

IP.com Disclosure Number: IPCOM000114386D
Original Publication Date: 1994-Dec-01
Included in the Prior Art Database: 2005-Mar-28
Document File: 2 page(s) / 49K

Publishing Venue

IBM

Related People

Ioki, K: AUTHOR [+2]

Abstract

This article describes a Digital Oscillator which consists of transparent latches and oscillates only when all clocks are active. When the personal computer system goes into suspend mode, the delay of the circuit is measured and the feedback point is determined. As a result, this digital circuit provides a fixed frequency.

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This is the abbreviated version, containing approximately 74% of the total text.

Digital Oscillator Adjusted by the Reference Clock

      This article describes a Digital Oscillator which consists of
transparent latches and oscillates only when all clocks are active.
When the personal computer system goes into suspend mode, the delay
of the circuit is measured and the feedback point is determined.  As
a result, this digital circuit provides a fixed frequency.

      In this circuit, many transparent latches and an inverter are
connected as shown in Fig. 1.  Only when all clocks are activeted,
this circuit oscillates.  The frequency of this oscillator is related
with a feedback point.  In the calibration phase of the operation,
reference clock is used to select a feedback point.  In order to get
fixed frequency regardless of the system environment, the calibration
is done each time the system goes into suspend mode.

The calibration process is illustrated in Fig. 2 and described below.
  1.  All latches are cleared, and all clocks are deactivated.
  2.  Set the data input of the first latch to one.  All latch
outputs
       are still zero at this time.
  3.  Assert a fixed length pulse on all clocks.  While the clocks
are
       active, the data is propagated through the latch chain.  Then
the
       falling edge of the clock pulse stops the data propagation.
The
       data propagation speed depends on the delay of the circuit.
The
       clock pulse is generated from the reference clock which is to
be
...