User guide

Understanding Error Detector Input Ports
The error detector has the following input ports:
• Clock In
This port needs to be connected to a clock signal unless you use the error
detector in Clock Data Recovery (CDR) mode, where it derives the clock
frequency from the data port. See “Clock Setup - Concepts ” on page 173 for
more details.
• Data In and
Data In
This port is connected to the data signal and the inverted data signal.
• Gate In
This port has two different functions.
– In normal mode it can be used to enable and disable the error counter. Errors
are only counted when this signal is low.
The error counter can only count errors in 128-bit data blocks. Thus, the
signal at the Gate In port must be low for at least 128 bits to enable the
counter. The following figure illustrates the effect of error gating. Errors are
only counted in the gray blocks.
Gate In
Expected Data on
Data Input
minimum signal
length not matched
only 128bit
granularity
A A
– The burst sync mode is a special operating mode for measuring data in
bursts of bits, rather than one continuous stream of bits.
In this case, the signal at the Gate In port controls the timing of
synchronization and error counting for each burst.
Understanding Error Detector Output Ports
The error detector provides several output ports that are used to connect it to other
devices for further error analysis:
• Trigger Out
Use this port to send a trigger signal to another connected device, such as an
oscilloscope.
• Error Out
This signal can be used to trigger an external instrument to help in error
analysis. When any number of errors are located within a 128-bit data block, a
Setting up the Error Detector 5
Agilent J-BERT N4903B High-Performance Serial BERT 169