Tektronix 071-0590-00 user manual Auto Search With Prbs Patterns

Reference

LOCK Indicator and Actions Taken by the Analyzer if

Synchronization (Lock) is Lost

The LOCK LED indicates whether or not BER is above or below the current synchronization threshold. The LOCK indicator will turn on while BER is below the current synchronization threshold, and off while BER is above this threshold. The setup actions taken by the Analyzer when BER crosses the synchronization threshold will depend on the state of the AUTO SEARCH and DISABLE keys, as shown in the table below.

Table 3-4. Actions Taken by Analyzer when Synchronization is Lost

AUTO SEARCH	DISABLE	Action when synchronization is lost (LOCK LED turns off)
on	off	Analyzer will attempt to find new pattern alignment, input level, input
		delay, PRBS pattern and pattern polarity
off	off	Analyzer will attempt to find new pattern alignment.
off	on	No setup change—Analyzer will continue to measure BER and count
		errors.
on	on	(this combination not allowed)

AUTO SEARCH With PRBS Patterns

When using a PRBS pattern you can enable the AUTO SEARCH feature as follows:

1.Set up the Generator to transmit a PRBS pattern.

2.Set up the Analyzer as follows: EXT (ref. data input control), off

SYNC DISABLE, off

AUTO SEARCH, on

After you perform this procedure, the auto-search feature will be enabled and the instrument will immediately attempt to re-synchronize with the received test signal. Once lock is achieved—that is once BER goes below the synchronization threshold—the BIT and PHASE history indicators will be cleared (turned off) and all current error counts will be reset to zero. The SYNC LOSS indicator will remain on, however, until cleared by the user.

NOTE: The AUTO SEARCH feature will work over a wide range of conditions. Therefore if you have set up the Generator to generate a standard PRBS, enabled the AUTO SEARCH feature on the Analyzer, but the Analyzer LOCK LED still fails to turn on, then it is likely that a problem exists in the device under test or your patch cord connections.

3-20 GB1400 User Manual