User Manual

Dante Controller User Guide

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network clock, its frequency must be 'pulled' up or down to match the frequency of the master clock. The

amount that the clock's frequency is pulled is referred to as 'offset'.

Hardware clocks can only support a certain amount of offset, referred to as 'pull range'. If the pull range is

exceeded, the slave clock will lose sync with the master clock, and the device will be automatically muted.

Software clocks typically use an algorithm to derive a clock from an internal counter. Software clocks can

support any amount of offset.

Rapidly-changing offset can also cause a slave clock to lose sync with the master clock.

Various factors can destabilise slave clocks by affecting their offset, such as:

n Overloaded network links

n Poorly-implemented EEE (Energy EfficientEthernet)

n A master clock that is derived from an inaccurate external word clock (one that does not run at its

nominal frequency)

About the Histogram

The horizontal axis of the histogram shows the distribution of clock frequency offset measurements

against the nominal frequency of the clock, in parts per million (ppm). The zero point of the horizontal axis

corresponds to the clock's nominal frequency (i.e. the frequency that the clock is intended to run at - for

example, 98kHz).

The vertical axis shows the number of measurements recorded at each data point, on a logarithmic scale.

The histogram is continually updated, with measurements taken roughly once per second.

n To select devices, click the drop-down menu at the top .

n To clear the histogram, click Clear.

n To save a png format screenshot of the current data, click Save.

Interpreting the Histogram

The histogram can be seen as an indication of how much work a slave clock is doing to stay in sync with

the master clock.