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Oscillator Switchover Method without External Control Lines

IP.com Disclosure Number: IPCOM000106233D
Original Publication Date: 1993-Oct-01
Included in the Prior Art Database: 2005-Mar-20
Document File: 2 page(s) / 58K

Publishing Venue

IBM

Related People

Adams, JS: AUTHOR [+2]

Abstract

A method for switching between three (3) oscillator signals is disclosed. The switch is accomplished without any external control signals and may be extended to include more than three oscillators signals. The circuit to accomplish the switchover is shown in the Figure.

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This is the abbreviated version, containing approximately 72% of the total text.

Oscillator Switchover Method without External Control Lines

      A method for switching between three (3) oscillator signals is
disclosed.  The switch is accomplished without any external control
signals and may be extended to include more than three oscillators
signals.  The circuit to accomplish the switchover is shown in the
Figure.

      Initially all oscillator signals are turned off (at either a
'1' or '0' level).  Gates A3, B3, and C3, whose function is described
in [*], sense that they have no signals and provide a '1' level to
gates A1, B1, and C1, and a '0' level to gates A4, B4, and C4.  A1,
B1, and C1 are now enabled to allow signals to pass thru to gates A3,
B3, and C3.

      One of the three(3) oscillators is now turned on.  OSC1 will be
used as an example.  After the first oscillator transition, gate A3
senses it has an oscillator and sends a '0' level to gates B1 and C1,
thus fencing OSC2 and OSC3 from being selected.  It also sends a '1'
level to gate A4 which when inverted becomes a '0' and enables gate
A6 which passes OSC1 thru to OSC$.

      A switchover from OSC1 to OSC2 or OSC3 would take place as
follows.  First, turn on OSC2 or OSC3 in order to reset their gates 4
and 5.  Then, turn off OSC1 at its source.  When gate A3 detects the
loss of OSC1, it will send a '1' to gates B1 and C1 enabling OSC2 or
OSC3 to pass thru to its gates 3 and 6.  Gate 6 however is disabled
by gate 5 which is still a '1'.  After the first tran...