:DIFF:CRECovery:CFRequency:MODE

:DIFF CRECovery Commands

Command Syntax

:DIFFN:CRECovery:CFRequency:MODE {AUTomatic | SAUTomatic | MANual}

Where N identifies a specific differential waveform in the form "<connection1-8>_<ch1|ch3|ch5|ch7>". With connection 1, the connection number part (that is, "1_") is optional, and you can simply use the channel number "<ch1|ch3|ch5|ch7>". When two channels are paired to create a differential waveform and a common-mode waveform, the odd-numbered channel is used when specifying the waveform. For example, connection 5 differential waveform 3 (from the pairing of channels 3 and 4) is DIFF5_3.

Query Syntax

:DIFFN:CRECovery:CFRequency:MODE?

Description

Sets the Constant Frequency CDR Mode option for the Constant Frequency clock recovery mode.

AUTomatic
(Automatic) — Fully automatic constant frequency clock recovery does not require you to enter any information about the signal.
The algorithm looks for the narrowest pulse in time and presumes it is an isolated one or zero. (For signals with a lot of inter-symbol interference (ISI), a particularly narrow pulse width can throw off this algorithm, giving a nominal data rate that is too fast.)
The algorithm then determines the number of bits in other pulse widths based on this time to determine the number of bits in every width.
SAUTomatic
Semi-automatic constant frequency clock recovery lets you "seed" the algorithm by entering the nominal data rate yourself. This allows the algorithm to run faster because it does not need to make two passes through the data.
The algorithm then computes the average actual bit width and computes the number of bits in every pulse accurately.
The symbol rate you enter (using the :DIFF:CRECovery:SRATe command) is the seed for the algorithm.
MANual
The symbol rate you provide (using the :DIFF:CRECovery:SRATe command) is used.
The symbol rate you enter should be the reciprocal of the unit interval for your serial data stream.

With either the AUTomatic or SAUTomatic options, the actual data rate and clock phase is measured such that the mean Time Interval Error (TIE) is 0. From this, the recovered clock is created.

Example Command Sequence

:DIFF1:CRECovery:MODE CFRequency
:DIFF1:CRECovery:CFRequency:MODE AUTomatic