STC5230_15 Datasheet, PDF (21/64 Pages) Connor-Winfield Corporation – Line Card Clock

STC5230
Synchronous Clock for SETS
Data Sheet
user to select the manually acceptable reference fre-
quency for all the reference inputs, at the integer mul-
tiple of 8kHz (Nx8kHz, N is integer from 1 to 32767).
Hence the manually acceptable reference frequency
range is integer multiple of 8kHz from 8kHz to
262.136MHz. When a manually acceptable reference
frequency is used, the user need to access the regis-
ter Ref Index Selector and Manual Accept Ref
Freq. Each input is monitored for frequency offset
between input and the internal freerun clock. The fre-
quency offset is shown in the register Ref Info when
associate reference index is selected at the register
Ref Index Selector.
Activity Monitoring
Activity monitoring is also a continuous process which
is used to identify if the reference input is in normal. It
is accomplished with a leaky bucket accumulation
algorithm, as shown in Figure 3. The “leaky bucket”
accumulator has a fill observation window that may
be set from 1 to 16ms, where any hit of signal abnor-
mality (or multiple hits) during the window increments
the bucket count by one. The leak observation win-
dow is 1 to 16 times the fill observation window. The
leaky bucket accumulator decrements by one for
each leak observation window that passes with no
signal abnormality. Both windows operate in a con-
secutive, non-overlapping manner. The bucket accu-
mulator has alarm assert and alarm de-assert
thresholds that can each be programmed from 1 to
64.
Fill Observa-
tion Window,
1ms ~ 16ms
alarms of all the references. Otherwise, a non-zero
bucket size must bFeugnrecattieorntahlanSpoer ceiqfiucaal ttioonthe
alarm assert threshold value, and the alarm assert
threshold value must be greater than the alarm de-
assert value. Attempted writes of invalid values will be
ignored. Therefore, the user, when re-configuring the
activity monitor, must carefully plan an appropriate
sequence of writes.
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 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, a qualification timer
may be programmed from 0 to 63 seconds by writing
to register Qualification Timer. The pull-in range is
the same as the disqualification range.
Activity Alarm
Asserted
Activity
Not Good
Activity Alarm
De-Asserted
Activity Alarm
Asserted
Frequency
Ref
Detector
Pulse
Monitor
Leaky
Bucket
Accumulator
Alarm Assert
Alarm De-Assert
Leak Observation
Window, 1~16 x Fill
Observation Window
Within Offset Qualification
Range for more than
Qualification Time
Activity
Good
Qualified
Out of Disqualification Range
Figure 3: Activity Monitor
Figure 4: Reference Qualification Scheme
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.
The user can set the bucket size equal to 0 to turn off
the activity monitor. This de-asserts the activity
The frequency offset of each reference is relative to
the digitally calibrated freerun clock may be read by
selecting the reference in the Ref_Selector register
and then reading the offset value from register Ref
Frq Offset.
Figure 4 shows the reference qualification scheme. A
Page 21 of 64 TM102 Rev: 3.0
© Copyright the Connor-Winfield Corp. All Rights Reserved Specifications subject to change without notice
Date: September 14, 2011