Trigger

Instrument
DCA-X
N109X
Flex Apps:
FlexDCA

Introduction

This topic describes both standard and pattern triggering of a DCA-X.

The information on triggering and pattern lock does not apply when FlexRT is enabled in FlexDCA. Triggering and pattern lock is not needed or used in FlexRT.

To Trigger the Instrument

A trigger signal must be provided to the instrument using one of the following methods:

  • Connect a synchronous clock signal to the instrument's front-panel Trigger connector. Click Setup > Trigger to open the Trigger dialog box and specify Front Panel. This is the most often-used method (as well as the default) source for triggering. You can also press the instrument's front-panel Trigger Level knob to select Front Panel. After connecting and then selecting the trigger source click Auto Scale on the menu bar to set the trigger level to the amplitude midpoint of the trigger signal. To manually adjust the trigger level, turn the Trigger Level knob.
  • On N109x-series DCA-M scopes, connect the clock signal to the DCA-M's front-panel Clock In connector.
  • If a trigger signal is not available, use clock recovery to recover the clock. Click Setup > Trigger and select Left Module or Right Module to trigger from the clock recovery module. Compatible modules (that have front-panel trigger input connectors) include N1060A, 86108A/B, N107x series DCA-M, and 83496A/B modules. When an 86108A/B precision waveform analyzer module is installed, the Left Module setting selects triggering from the recovered clock and the Right Module setting selects triggering from the precision timebase. I you are using an 86107A Precision Timebase module and the time reference is set, all external trigger sources and controls are disabled.
  • Trigger on the data input to a module. Split the incoming data signal and route half of the data to the instrument's trigger input. Route the other half to the module's input connector. Due to jitter and pattern dependencies this technique shows incomplete eye diagrams and approximately 75% of waveforms are never observed in a PRBS.
  • In Oscilloscope and Eye/Mask modes, you can also select Free Run. This selection causes the instrument to trigger as soon as the trigger is armed; an external trigger is not used. Free run is asynchronous to the data and can be used to quickly examine a signal's amplitude without any timing information.

83496A MODULES. When using an 83496A module to recover the clock, if the symbol rate is below 400 MBd, the instrument must be triggered from the front panel rather than the 83496A's rear-panel connector. Connect the module's front-panel Recovered Clock Out to the mainframe's front-panel Trigger input.

Special Case: Triggering 86100D-STR

If you are using a 86100D-STR (standard-trigger) with a clock recovery or 86108A Precision Waveform Analyzer module, you must connect a cable between the module's clock output port to the 86100D's Trigger input connector as shown in this picture. The following table describes the output port for each type of module. In addition to connecting the cable, press the 86100D's front-panel Trigger Level knob to select the Front Panel Trigger input. This cable is not required on 86100-ETR enhanced-trigger instruments.

Module Clock Output Ports
Module Output Port Description
86108A
Precision Waveform Analyzer
Recovered Clk Output Full rate output for symbol rates ≤7.1 GBd. Half rate output for symbol rates > 7.1 GBd
83491/2/3/4A
Clock Recovery
Clock Full rate output. Selected symbol rate must be below 3.2 GBd.
83495A
Clock Recovery
Recovered Clock Out Output rate is too high for 86100D-STR front-panel Trigger input.
83496A/B
Clock Recovery
Recovered Clock Output Output rate divide ratio is user selectable from 1 to 16 (≤ 7.1 GBd) and 2 to 16 (7.1 to 13.5 GBd). In clock recovery setup, ensure that divide ratio results in output rate below 3.2 GBd.

Special Case: Triggering 86100D-STR with 54754A TDR

If you are using a 86100D-STR (standard-trigger) with a 54754A TDR/TDT module, you must connect a cable between the module's Trigger output port to the 86100D-STR's Trigger input connector as shown in these pictures.

Triggering with One TDR Module

If two 54754A TDR modules are used, add an 11667B Power Splitter or 11636B Power Divider and combine the triggers as shown in the picture.

Triggering with Two TDR Modules