Hardware-Generated Prbs - Agilent Technologies N4906B Serial BERT User Manual

Hardware-Generated PRBS

Agilent N4906B Serial BERT, User's Guide, October 2005
Hardware-Generated PRBS
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).
How the Hardware Generates PRBS
2^n –1 PRBS is an inverted, hardware-generated pattern that is
created by a series of shift registers with adjustable feedback. The
example below shows the register configuration for a 2^7 –1 (127-bit)
pattern.
The following table describes the operation of XOR'ing two points for
the different patterns.
Sequence Length Shift-Register Configuration
7 7
2 -1 D
10 10
2 -1 D
11 11
2 -1 D
15 16
2 -1 D
23 23
2 -1 D
31 31
2 -1 D
6
+ D + 1 = 0, inverted
7
+ D + 1 = 0, inverted
9
+ D + 1, inverted
14
+ D + 1 = 0, inverted
18
+ D + 1 = 0, inverted
28
+ D + 1 = 0, inverted
Setting up Patterns
49