# Pseudo random binary signal

They're random-ish streams of bits that can be easily and reliably reproduced using very simple hardware or software. Any semiconductor that can be used to transmit information can be tested at a functional level with a PRBS.

Send a PRBS to the device you're testing, tell the device to repeat it back to you, and compare what you received to what you sent. A PRBS is preferred over a simple square wave because it stresses the device under test in more ways.

It's not uncommon for a device to have no problem transmitting a sequence like "" but choke on a sequence with repeated bits like "". PRBSs include strings of repeated bits as well as strings of alternating bits.

These polynomials are elements of GF 2 n the Galois Field of two elements. These polynomials can also be represented as binary numbers:. First, a seed polynomial is chosen. Zero can't be chosen as a seed state because the seed is multiplied by x to produce the next state. If the seed is zero, this product is zero and there is no next state.

Note that this method produces the states in reverse order when compared with the code given later in this post. PRBSs include strings of repeated bits as well as strings of alternating bits.

These polynomials are elements of GF 2 n the Galois Field of two elements. These polynomials can also be represented as binary numbers:. First, a seed polynomial is chosen.

Zero can't be chosen as a seed state because the seed is multiplied by x to produce the next state. If the seed is zero, this product is zero and there is no next state. Note that this method produces the states in reverse order when compared with the code given later in this post.

Here's an example of the math worked out by hand:. PRBSs produce 2 n -1 bits before repeating. Photo by Vladimer Shioshvili. Why are PRBSs useful? What are some common PRBSs?