Clock Design - Symmetricom TimeCreator 1000 User Manual

Clock Design

The TimeCreator 1000 clock design includes a highly stable ovenized Quartz crystal
to produce accurate synchronization outputs. In a dual-IOC configuration, the clock
function is redundant to provide protection. Each IOC qualifies the input signal and
filters jitter and wander noise elements that may exist. In the event that all input
references are lost or disqualified, the unit goes into holdover mode with the
oscillator providing the system reference.
The IOC meets Type III performance.
Operating Modes
The TimeCreator 1000 has the following operating modes:
Warm-up – The period immediately following power-up that allows local

oscillator stabilization required for stable frequency generation from the system.
Free-run – This operating mode allows the system to generate a DTI output that

has stable generation of frequency and TOD when the system has no external
frequency reference (GPS or DTI). TOD can be from NTP, a user-specified time,
or from the IMC's real-time clock.
Fast-Lock (Acquire) – In this mode the system quickly locks the local oscillator

frequency to another frequency source (GPS or DTI reference) to establish the
system's frequency and TOD.
Normal (Locked) – In this operating mode, the system's output frequency and

TOD are tracking the reference frequency (GPS or DTI) and TOD within the DTI
specified requirements.
Bridging – If all input references are lost, the TimeCreator 1000 goes into

bridging mode. In this mode, the outputs continue to provide accurate timing for a
limited period. If the system qualifies the reference prior to the end of the bridging
time, the system re-enters Fast-Lock or Normal operation mode. If the inputs are
not re-qualified before the bridging time has elapsed, the TimeCreator 1000
enters holdover mode.
Holdover – If the reference signal is lost and not re-qualified when the bridging

time elapses, the clock enters holdover mode. The accuracy of the TimeCreator
1000 output is then dependent on the quality level of the oscillator.
Extended Holdover – If the clock remains in holdover for an extended duration,

typically 4 hours, the clock enters extended holdover mode.
097-93100-01 Revision C – February, 2010
Chapter 1 Overview of the TimeCreator 1000
TimeCreator 1000 User's Guide
Overview
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