User's Guide

7 Web Page Reference
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Daylight Saving
See Section 7.10.9 “Setting the clock”
7.11 Diagnostics Plotter
For the PTP 500 Series, the storage of link performance histograms is set to 31 days worth of
data. To optimize RAM (volatile memory) usage of a cascading histogram approach has been
adopted. The data is stored for one hour at a resolution of one second. The histograms use a
cascading approach to daisy chain multiple histograms together. When the first histogram fills
up the overflow from the first is used as an input to the next histogram in line. To optimize
memory utilization, a statistical analysis is performed on the overflow to reduce the amount of
data to be stored. The cascading histograms are defined as:
• Histogram 1: 1 hour at a resolution of 1 second
• Histogram 2: 24 hours at a resolution of 1 minute
• Histogram 3: 30 Days at a resolution of 1 hour
For example, when histogram 1 fills up and starts to overflow the first minute of overflow is
analyzed and the maximum, minimum and mean over that minute are computed and inserted
into histogram 2. When histogram 2 fills up and starts to overflow the first hour of overflow is
analyzed and the maximum, minimum and mean over that hour is computed and inserted into
histogram 3. When histogram 3 starts to overflow, the overflow data is simply discarded.