Agilent Technologies J-BERT N4903, User Manual

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During test run, the Serial BERT always sends out all blocks of a pattern.
In the case of the 192-bit pattern mentioned above, the pattern is
repeated 8 times when sent out (in effect, making it a 1536-bit pattern).
The same behavior of repeating a pattern to fill up complete blocks also
applies to alternating patterns. In this case, each half of the pattern is
loaded into a separate location in the RAM. When an alternating pattern
is generated, first all blocks of pattern A are sent, then all blocks of
pattern B are sent, and so on.
A0 A1 A2 B0 B1 B2 A0 A1 A2
A A A A A A A A B B B B B B B B A A A A A A A A
Implications of Using Memory-Based Patterns
There are several implications to the way Serial BERT handles memory-
based patterns, a few of which are:
•
If you set up an alternating pattern where pattern B is a replica of
pattern A except for the addition of one error, and the pattern is an
odd number of bits long, the error will be repeated 512 times when
B is sent (because pattern B is sent 512 times before switching back
to A).
•
If you want to send a periodic pattern, you only have to define a
single repetition. For example, if you want to send alternating 1's
and 0's, you only have to define the first two bits. This pattern is
automatically loaded 256 times to fill up a complete block of RAM.
•
If you set up a trigger to be generated whenever a pattern is sent, the
trigger is sent whenever all blocks that store this pattern have been
sent (and not every time the pattern is sent).
So, for example, if you have a standard pattern that is 384 bits long,
this pattern must be loaded into the memory four times to reach the
512-bit boundary. A trigger would then be generated every
4x384bits, or 1536bits.
2
Setting up Patterns
32 Agilent J-BERT N4903 High-Performance Serial BERT
How the Serial BERT Handles
Alternating Patterns