STC5428 Datasheet, PDF (26/66 Pages) Connor-Winfield Corporation – Synchronous Clock for SETS

Fill Observa-
tion Window,
1ms ~ 16ms
STC5428
Synchronous Clock for SETS
DATASHEET
time may be programmed from 0 to 63 seconds by
writing to register QuFaulinficctaitoionnaSl oSapkeincgifTicimatei.oTnhe
pull-in range is the same as the disqualification range.
Frequency
Ref
Detector
Pulse
Monitor
Leaky
Bucket
Accumulator
Alarm Assert
Alarm De-Assert
Activity
Not Good
Leak Observation
Window, 1~16 x Fill
Observation Window
Activity Alarm
Asserted
Activity Alarm
De-Asserted
Activity Alarm
Asserted
Figure 2: Activity Monitor
Applications can write to the following registers to
configure the activity monitor: Fill Obs Window,
Leak Obs Window, Bucket Size, Assert Threshold,
and De Assert Threshold.
Continuously
Within Offset Qualification
Range for more than
Qualification soaking Time
Activity
Good
Qualified
Setting the bucket size to 0 will bypass the leak
bucket accumulator and assert or de-assert the activ-
ity alarm based on results of frequency detector and
pulse monitor only. A non-zero bucket size must be
greater than or equal to the alarm assert threshold
value. The alarm assert threshold value must be
greater than the alarm de-assert threshold value and
less than or equal to the bucket size value. Attempted
writes of invalid values will be ignored. Therefore,
user must carefully plan an appropriate sequence of
writes when re-configure the activity monitor. See
register Bucket Size, Assert Threshold and De
Assert Threshold for details.
Alarms appear in the Refs Activity register. A “1”
indicates activity, and a “0” indicates an alarm, no
activity. Note that if a reference is detected as a differ-
ent frequency, the leaky bucket accumulator is set to
the bucket size value and the reference will become
inactive immediately.
Input Qualification
A selected reference is “qualified” if it passes the
activity evaluation and its frequency offset is within
the programmed qualification range for over a pre-
programmed soaking time.
A reference qualification range may be programmed
up to 102.3 ppm by writing to register Qualification
Range, and a disqualification range set up to 102.3
ppm, by writing to register Disqualification Range.
The qualification range must be set less than the dis-
qualification range. Additionally, qualification soaking
Out of Disqualification Range
Figure 3: Reference Qualification Scheme
The frequency offset of each reference is relative to
the internal freerun clock may be read by selecting
the reference in the Ref Index Selector register and
then reading the offset value from register Ref Info.
The frequency offset of the internal freerun clock can
be calibrated by writing to the register Freerun Cali.
Figure 3 shows the reference qualification scheme. A
reference is qualified if it has no activity alarm and is
continuous within the qualification range for more
than the qualification soaking time. An activity alarm
or frequency offset beyond the disqualification range
will disqualify the reference. It may then be re-quali-
fied if the activity alarm is off and the reference is
within the qualification range for more than the qualifi-
cation time.
The reference qualification status of each reference
may be read from register Ref Qual.
Automatic Reference Election Mechanism
The STC5428 has an auto reference elector always
elect the best candidate from the reference inputs
according to the revertive status, each reference’s pri-
ority and qualification. T0 and T4 have independent
priority tables for automatic reference selection.
Regardless what the current reference selection
mode is (automatic, manual, or hard-wired manual),
Page 26 of 66
Preliminary
Rev: 0.2
© Copyright the Connor-Winfield Corp. All Rights Reserved Specifications subject to change without notice
Date: April 3, 2014