User guide

Data Delay
The data input delay defines the point in time (in reference to the clock signal) at
which the incoming data signal is measured. Specifically, it is the time delay from
the active clock edge to the time at which the data is actually sampled.
This field allows the manual entry of the data input delay, and displays the current
value in picoseconds. This delay can be set as high as 1 bit period or 10 ns (10,000
ps), whichever is less.
You can adjust the data input delay in the following ways:
• Click inside the text field and use the numeric keypad or front panel knob to
enter a value.
• Click anywhere in the sampling point display. The sampling point will be moved
to that location.
• Turn the Data In Delay knob on the front panel. A small window will appear,
displaying the delay value. This knob can be used at any time, while in any
window.
Clock Falling Edge
Activate this checkbox to move the sampling point from the rising edge to the
falling edge of the clock signal. This function is useful when the maximum data
input delay adjustment is not large enough to move the sampling point to the
desired location. This occurs at very low frequencies only. See “Bit Rate Range”
on page 176 for more information.
Auto Align
Click this button to automatically set the optimum sampling point.
This routine will not stop if the optimum sampling point cannot be found. If no
optimum sampling point is found after a reasonable time, you can click Cancel.
The status message bar will indicate if this function is unsuccessful.
The following settings may affect the result of the auto align function:
•
Data Inverted
•
BER Threshold
N O T E
In SER mode, the Auto Align with CDR enabled supports the ED frequency above
11.5 Gb/s and performs Data Centre with appropriate threshold settings.
T I P
Alternatively, you can also press the Auto Align button on the front panel.
Setting up the Error Detector 5
Agilent J-BERT N4903B High-Performance Serial BERT 199