ACS8509 Semtech Corporation, ACS8509 Datasheet - Page 38

• Manufacturer Part Number: ACS8509
• Description: Synchronous Equipment Timing Source for Sonet or SDH Network Elements
• Manufacturer: Semtech Corporation

Figure 9 Inactivity and Irregularity Monitoring
Leaky Bucket Timing
The time taken (in seconds) to raise an inactivity alarm on
a reference source that has previously been fully active
(Leaky Bucket empty) will be:
where n is the number (0 to 3) of the Leaky Bucket
Configuration. If an input is intermittently inactive then
this time can be longer. The default setting of
cnfg_upper_threshold_n is 6, therefore the default time is
0.75 s.
The time taken (in seconds) to cancel the activity alarm on
a previously completely inactive reference source is
calculated, for a particular Leaky Bucket, as:
where:
Revision 2.00/January 2006 © Semtech Corp.
ADVANCED COMMUNICATIONS
Alarm
Reference
Source
Leaky
Bucket
Response
(cnfg_upper_threshold_n) / 8
[2
a = cnfg_decay_rate_n
b = cnfg_bucket_size_n
c = cnfg_lower_threshold_n
(where n = the number (0 to 3) of the relevant
Leaky Bucket Configuration in each case).
(a)
x (b - c)]/ 8
Inactivities/Irregularities
Programmable Fall Slopes
FINAL
Page 38
Activity Monitoring
The ACS8509 has a combined inactivity and irregularity
monitor. The ACS8509 uses a “leaky bucket”
accumulator, which is a digital circuit which mimics the
operation of an analog integrator, in which input pulses
increase the output amplitude but die away over time.
Such integrators are used when alarms have to be
triggered either by fairly regular defect events, which
occur sufficiently close together, or by defect events
which occur in bursts. Events which are sufficiently
spread out should not trigger the alarm. By adjusting the
alarm setting threshold, the point at which the alarm is
triggered can be controlled. The point at which the alarm
is cleared depends upon the decay rate and the alarm
clearing threshold. On the alarm setting side, if several
events occur close together, each event adds to the
amplitude and the alarm will be triggered quickly; if events
occur a little more spread out, but still sufficiently close
together to overcome the decay, the alarm will be
triggered eventually. If events occur at a rate which is not
sufficient to overcome the decay, the alarm will not be
triggered. On the alarm clearing side, if no defect events
occur for a sufficient time, the amplitude will decay
gradually and the alarm will be cleared when the
amplitude falls below the alarm clearing threshold. The
ability to decay the amplitude over time allows the
importance of defect events to be reduced as time passes
by. This means that, in the case of isolated events, the
ACS8509 SETS
(all programmable)
F8530D_026Inact_Irreg_Mon_02
bucket_size
upper_threshold
lower_threshold
DATASHEET
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