Tektronix 071-0590-00 user manual Applications, Two Auto Search Synchronization Methods

Applications

Application Note

Method For Very Fast Automatic Receiver Synchronization And Eye Width Measurement

Two Auto Search Synchronization Methods

This application note describes two Auto Search synchronization methods used in the GB1400 Bit Error Rate test set - a FAST method and a BER method. The criteria and sequence of events for the two methods are compared and the differences are described.

Auto Search is the feature that the GB1400 uses to describe its method of automatic setup and synchronization. Both methods of Auto Search synchronization perform the following functions, but in different ways and with differing results depending on the type of data and its quality.

∙Analysis of the input data signal amplitude to select the correct threshold voltage.

∙Determine the timing skew between the clock and data signals and automatically optimize it.

∙Determine the correct data sequence and whether it is inverted.

∙Measure the data eye width.

So that the following explanations are clear, let us first define some terms.

V–THRESHOLD

This is the absolute DC level above which GB1400 Receiver will declare a data bit value of “1” (HIGH). Below this value, it is considered to be a “0” (LOW).

DELAY

This is the timing difference (skew) between ideal timing and actual timing between the incoming clock and data. Ideal timing will place the falling edge of the clock signal in the center of the data bit. Any deviation from the ideal should, when possible, be corrected by delaying either the clock or the data (as in the GB1400 Receiver) in relation to each other.

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