STC5230 Datasheet, PDF (16/48 Pages) Connor-Winfield Corporation – Synchronous Clock for SETS

STC5230
Synchronous Clock for SETS
Data Sheet
threshold value, and the alarm assert threshold value
must be greater than the alarm de-assert value.
STC5230 will ignore the writing to these three regis-
ters if the value violates the rules. User shall carefully
plan the scenario of activity monitor re-configuration.
Alarms appear in the Refs_Activity register
(0x18,0x19). A “1” indicates activity, and a “0” indi-
cates an alarm, no activity. Note that if a reference is
detected as a different frequency, the leaky bucket
accumulator is set to the bucket size value and the
reference will become inactive immediately.
Figure 4 shows the reference qualification scheme. A
reference is qualifiedFiuf nit chtaisonnoaal cStipvietycaiflaicrmataiondnis
within the qualification range for more than the qualifi-
cation time. An activity alarm or frequency offset
beyond the disqualification range will disqualify the
reference. It may then be re-qualified if the activity
alarm is off and the reference is within the qualifica-
tion range for more than the qualification time.
The reference qualification status of each reference
may then be read from register Refs_Qual (0x1a/1b).
Reference inputs are also monitored and qualified for
frequency offset.
A reference qualification range may be programmed
up to 102.3 ppm by writing to register
Qualification_Range (0x12,0x13), and a disqualifi-
cation range set up to 102.3 ppm, by writing to regis-
ter Disqualification_Range (0x10,0x11). The
qualification range must be set less than the disquali-
fication range. Additionally, a qualification timer may
be programmed from 0 to 63 seconds by writing to
register Qualification_Timer (0x14). The pull-in
range is the same as the disqualification range.
Active Reference Selection
The T0 and T4 timing generators may be individually
operated in either manual or automatic input refer-
ence selection mode. The mode is selected via the
T(0/4)_Control_Mode registers (0x1c/0x39).
Manual Reference Selection Mode
In manual reference selection mode, the user may
select the reference. This mode is selected via the
T(0/4)_Control_Mode (0x1c/0x39) registers. The ref-
erence is selected by writing to the T(0/
4)_Manual_Active_Ref (0x1f/0x3c) registers.
The frequency offset is centered at the digitally cali-
brated freerun clock. Each value of may be read by
selecting the reference in the Ref_Selector register
(0x15) and then reading the offset value from register
Ref_Frq_Offset (0x16,0x17).
Automatic Reference Selection Mode
In automatic reference selection mode, the device will
select one pre-qualified reference as the active refer-
ence. This mode is set via the T(0/4)_Control_Mode
(0x1c/0x39) registers.
Activity Alarm
Asserted
Activity
Not Good
Activity Alarm
De-Asserted
Activity Alarm
Asserted
Within Offset Qualification
Range for more than
Qualification Time
The active reference is picked according to its indi-
cated priority in the reference priority table, registers
T(0/4)_Priority_Table
(0x31~0x36/0x4e~0x53).
Each reference has one entry in the table, which may
be set to a value from 0 to 15. ‘0’ masks-out the refer-
ence, while 1 to 15 set the priority, where ‘1’ has the
highest, and ‘15’ has the lowest priority. The highest
priority pre-qualified reference then is a candidate to
be the active reference. If multiple references share
the same priority, the one who has be qualified with
longer duration will win the tie-break.
Activity
Good
Qualified
Out of Disqualification Range
This active reference candidate will be promoted to
be active reference immediately if no active reference
exists. The operating mode will then enter synchro-
nized mode.
Figure 4: Reference Qualification Scheme
If the candidate reference is different to the existing
active reference, this candidate may or may not revert
Preliminary
Data Sheet #: TM102 Page 16 of 48
Rev: P01
© Copyright the Connor-Winfield Corp. All Rights Reserved Specifications subject to change without notice
Date: August 22, 2007