Teledyne LeCroy Eye Doctor II - Manual (Page 31)

Operator's Manual
Decision Feedback Equalization (DFE)
To use the DFE:
1. Check the Enable checkbox in the Decision Forward Equalizer (DFE) section.
2. Specify the # Taps. The # Taps is set in order to span the # of UI the signal takes when settling to a
final value after a transition.
3. Specify the maximum number of unit intervals to use for training in Max UI's for Train. We suggest
leaving this value at 1000. Higher values make the training slower, and much lower values may
reduce the training accuracy.
4. Either check Auto Find Levels or manually enter the Upper Level, Lower Level and Decision Level.
5. Press the Train DFE button.
Note: The Include In Training checkbox allows the user to select whether or not the DFE is trained
when the Train FFE & DFE button is pressed on the Equalizer dialog.
While the best way to use the DFE is to train it, you can also enter the exact taps weights (if known) on
the DFE Details (as follows). The Clear Taps button sets all of the taps to 0. This is the pass-through state
for the DFE.
The Deskew control can be adjusted manually by the user or optimized when the DFE is trained. This
time plus 1/2 of a unit interval is the point at which the decision is made for the decision feedback equal-
izer. This is the same control as the Deskew control in the Clock Recovery dialog.
DFEs are prone to burst errors (meaning, once errors are created, they run for a long time). The DFE's pro-
pensity to create burst errors is based on the effectiveness of the DFE to aid in the accurate decoding of
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