Specifications

4-17
Operating Features and Specifications
Automatic Clock-to-Data Alignment
Automatic Clock-to-Data Alignment
Introduction
An important feature of the Agilent 70843 error detector is the ability to automatically
align the clock and data inputs such that the error detector samples in the middle of the eye
(in the time axis). This reduces setting-up time as it automatically compensates for delays
in the clock/data paths, preventing unnecessary errors.
The delay point in the eye at which the error detector samples can also be set manually
using the softkey (part of the menu of softkeys).
Definition
In order for the system to align the clock with the data (at the error detector input) it must
find the edges of the data input eye.Theeye edge is defined as a data input delay point
where the Bit Error Ratio (BER) measured over a decisecond interval is less than or equal
to a pre-defined threshold, and another adjacent point which is greater than the threshold.
The Eye Edge Threshold can be set by the user to any value between 10
-1
and 10
-7
either
via the softkey or remotely.
It is recommended that you perform the Clock-to-Data alignment procedure each time you
configure an Agilent 71612 Series error performance analyzer. Normally this would be
after setting up instrument parameters such as Pattern, Data Output (Level, Polarity) and
Data Input (0/1 threshold, polarity).
Eye Width
Each time a successful clock-to-data alignment procedure is performed the eye width is
calculated, and displayed on the EYE RESULTS page (select , then
. This result can be added to the USER'S PAGE.
NOTE The clock/data alignment process time is pattern-dependent, and with
some large user-patterns alignment can take several minutes. If you
wish to select a user pattern, it is recommended that you first perform
clock/data alignment on a pure PRBS. This does not affect alignment
accuracy and can save you valuable time.
NOTE Ensure that the received clock frequency is stable before performing a
clock-to-data alignment procedure.
DAT I/P DELAY
input & eye
EYE EDG THRSHLD
result pages
EYE RESULTS