Agilent Technologies J-BERT N4903, User Manual

Page: 111 / 434

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 116 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.
Setting up the Error Detector
4
Agilent J-BERT N4903 High-Performance Serial BERT 111