Specifications

2-10
Programming the HP 71612 Series
Device/Controller Synchronization Techniques
A recommended program control flow for the user to achieve this synchronization is given
below. It can be used with any combination of BERT modules, and the signal generator
source can be either slaved to the pattern generator or independent. It should be regarded
as a guideline only.
NOTE More detailed examples are included in the form of Basic Language
Programs in the Program Examples appendix at the rear of this manual.
These include details of how to program:
• the detection of clock stabilization following a frequency change,
• how to perform a clock to data delay alignment and
• how to test and gain pattern synchronization.
Although the sequence below is shown for a combined pattern generator and error
detector system, the steps to omit for generator or detector only systems are self evident.
When operating at a single frequency the clock stabilization and clock to data delay
alignment steps may also be omitted.
1. Set error detector to manual sync mode.
2. Setup signal generator.
3. Setup pattern generator.
4. Setup error detector.
5. If the clock source is not slaved to the error performance analyzer, then hold off further
commands until the pattern generator input clock frequency has stabilized, and the unit
is in the correct frequency band. For further details see SENSE6:FREQ? and
SENSE6:BAND? generator commands and SENSE2:FREQ? and SENSE2:BAND?
detector commands and also examples of there use in the detailed example at the rear of
this manual.
6. For reliable bit error measurements following any frequency change it is important to
configure the detector to sample the incomingdatapatternatthecenteroftheeyei.e.
midway between pattern bit transitions. Where the required delay has not previously
been established, a clock to data alignment should will find this optimum clock to data
delay setting and leave the detector configured this way in addition to measuring the
eye-width. For further details see the SENSE1:EYE detector commands and also exam-
ples of there use in the detailed example at the rear of this manual. When a successful
alignment is performed the synchronisation step below may be omitted otherwise the
cause of the alignment failure must be ascertained before continuing.
7. Synchronize the error detector to the incoming pattern. For further details see the
SENSE1:SYNC and STAT:QUES:COND? detector commands and also examples of
there use in the detailed example at the rear of this manual.
8. If sync is gained then proceed with the testing. If sync has not been achieved then the
cause must be established and understood before going any further.
NOTE Accessing large patterns can take several minutes. Control programs
must be prepared for I/O time-outs of this order.