User guide

Table 10
n Sequence Length Longest Run of 1's Longest Run of 0's
7 128 7 7
10 1,024 10 10
11 2,048 11 11
13 8,192 13 13
15 32,768 15 15
23 8,388,608 23 23
Zero Substitution Patterns
A potential risk to bit errors are longer rows of zeros within a data stream. The
longest run of zeros in a 2^n PRBS consists of n zeros.
The Zero Substitution function can be used to stress the DUT additionally by
inserting a longer row of zeros in the data stream. The length of the zero row can
be freely specified, up to the length of the pattern.
The following figure shows an example, where a run of 10 zeroes is inserted into
a PRBS 2^7 pattern.
*
ZRUNRun of 0s
0000000 1 01000100
00000010 0 0 0 00 11 0
PRBN
ZSUB
* Closing bit
Mark Density Patterns
The mark density of a pattern is the portion of bits that are ones.
A pure PRBS pattern contains an equal number of ones and zeros and, thus, has
an average voltage in the center between high and low level. Therefore, the mark
density of such a pattern is 1/2.
Some devices may have problems processing data streams with different mark
density as this results in other average voltages and, thus, different electrical
conditions.
3 Setting up Patterns
92 Agilent J-BERT N4903B High-Performance Serial BERT