User guide

The ones (mark) density can be varied to put the pattern out of balance in a
randomly distributed way. This may be useful for systems that are AC-coupled.
This helps to check for effects such as baseline wander.
To test these cases, the Serial BERT provides PRBS patterns with the mark
densities 1/8, 1/4, 1/2, 3/4, and 7/8.
Software-Generated PRBS - Procedures
The recommended way to load the data patterns to the pattern generator and error
detector is to use the Pattern Select Form dialog box.
See “Loading Patterns to the Pattern Generator and Error Detector” on page 73 for
details.
Software-Generated PRBS - Reference
Use the Pattern Select dialog box to select the pattern(s) you want to write to the
pattern generator and the error detector. See “Select Pattern Dialog Box” on page
89 for details.
Hardware-Generated PRBS
Hardware-Generated PRBS - Concepts
This section describes the basics of hardware-generated PRBS 2^n -1 patterns.
When to Test with Hardware-Generated PRBS Patterns
You can use the Serial BERT's hardware-generated PRBS patterns if you require
simple random traffic for testing your device. The 2^n -1 odd pattern lengths are
not related to the divided clock rate. When using an oscilloscope, this will ensure
that the random contents of the bit stream is sampled.
The spectral contents of PRBS 2^n -1 patterns and the special property of
decimation may also be useful in many applications (for example, for multiplexer
or demultiplexer testing).
Setting up Patterns 3
Agilent J-BERT N4903B High-Performance Serial BERT 93