Specifications

4-18
Operating Features and Specifications
Measurements
Automatic 0/1 Threshold Center
The 0/1 threshold center operation is used to set the 0/1 threshold midway between two
points, top and bottom of the eye, where the bit error ratio is equal to a selectable
threshold. The eye height is calculated and displayed (on the EYE RESULTS page). The
BER selectable threshold is set using the key.
The function can be used to determine the optimum sampling point
for asymmetric eyes, or on patterns with an unequal mark-density.
To perform a 0/1 Threshold Centering
Select then press .
Data Input 0/1 Threshold
Introduction
There are three methods of determining the 0/1 Threshold of input signals at the error
detector data input; they are Manual, Automatic Track and Automatic Center.
If the signal at the error detector data input is a standard PRBS or a clean signal (no
excessive noise or jitter) with a 1:1 mark density, use the Manual or Automatic Track
Modes, otherwise use the Automatic Center mode.
Manual: 0/1 threshold can be set manually.
Range: +1 to −3V nominal
Resolution: 1 mV nominal
Automatic Track: Tracks the mean dc level of the input signal. The 0/1 threshold
calculated is displayed.
Automatic Center: The error detector sets the 0/1 threshold midway between two points,
the top and bottom of the eye, where the bit error ratio is equal to a
selectable threshold. The eye height is calculated and displayed.
Measurements
The error detector counts bit errors by comparing data bit-by-bit with the internally-
generated reference pattern. All measurements run during the gating periods with the
exception of Delta Error Count and Delta Error Ratio. These measurements run
continuously to enable user adjustments for minimizing errors. The measurements are as
follows, (refer to Appendix A for measurement definitions):
EYE EDG THRSHLD
0/1 THR CENTER
input & eye
0/1 THR CENTER