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,QWHUQHWwww.lecroy.com

Copyright © July 1998, LeCroy. All rights reserved. Information in this publication supersedes allearlier versions. Specifications subject to change.

LeCroy, ProBus and SMART Trigger are registered trademarks of LeCroy Corporation. MathCad is aregistered trademark of MATHSOFT Inc. Centronics is a registered trademark of Data ComputerCorp. Epson is a registered trademark of Epson America Inc. PowerPC is a registered trademark ofIBM Microelectronics. MATLAB is a registered trademark of The MathWorks, Inc. DeskJet, ThinkJet,QuietJet, LaserJet, PaintJet, HP 7470 and HP 7550 are registered trademarks of Hewlett-PackardCompany. I2C is a trademark of Philips.

LCXXX-CKTRIG-OM-E Rev C 0898

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The External Clock/Trigger (CKTRIG) hardwareinstalled in your LeCroy digital instrument offersthese special capabil it ies:

À External Reference: phase-synchronization to an external10 MHz reference — either to match the stability of theexternal source, or to phase-lock the acquired signal. Severalinstruments can then be synchronized using a single sourceas reference. See next page.

À Trigger Comparator pulse generated each time a validtrigger condition* is encountered on the trigger signal —invaluable for event-counting and throughput applications.See page 7.

À External Clock for externally clocking at a fixed frequency†,enabling full phase control over the acquired signal. As well,the sample rate can be fine-tuned to the exact speedrequired for the application in hand. See page 13.

Thus CKTRIG can provide a uniquely high degreeof synchronization between instruments, andbetween the instrument and the externalenvironment.

* Edge Trigger only for all models except the LC564AND LC584SERIES OSCILLOSCOPES, AND DISK DRIVE ANALYZERS (DDAS),which offer this feature for SMARTÌ Triggers, too.† 50–500 MHz on all models except those in the LC564 ANDLC584 SERIES OSCILLOSCOPES, AND DISK DRIVE ANALYZERS

(DDAS): DC to 500 MHz.

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Instruments can be synchronized with an external, 10 MHz sine-wave or square-signal reference (Fig. 1). This reference caneven be used when an instrument’s channels are combined(see the instrument Operator’s Manual ). The reference’s inputsignal requirements are these:

À Amplitude: 800 mV p-p typical; 1.25 V p–p minimum forguaranteed switching

À Frequency Range: 10 MHz ± 5 %

À Offset: 0 V centered — any DC offset may require a larger inputswing

À Sampling Uncertainty: ± 100 mV slew-rate signal

À Input impedance: 50 Ω ± 5 %

À Maximum Input Voltage: ± 2.5 V.

Figure 1: External Reference signal.

Once such a reference signal is displayed, select “External” fromthe “UTILITIES” “SPECIAL MODES” menus (Fig.2). Then, usingthe “TIMEBASE” menus, display a screen similar to that shownbelow. To do this by remote control, use theREFERENCE_CLOCK command (see page 20).

Figure 2: Acquisition with 10 MHz external reference.

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6DPSOLQJ7LPH6WDELOLW\ The histogram graphs on the following pages (Figs. 3–4)illustrate the sampling-time stability when using a CKTRIGexternal reference to synchronize two LeCroy digital instruments.

Several acquisitions were made using the instruments, with andwithout an external reference. They were placed in the sameconfiguration, and the same input and trigger signals were usedby both, as shown in this diagram.

First, an acquisition was performed using the same input signal,with the two instruments set up in exactly the same configuration.

Next, the delay in sampling time between them (D) in radianswas extracted from their data using a PC.

These two steps were then repeated two hundred times.

Finally, histograms of D were created.

Note: to synchronize the instruments, D must be stable.

Instrument 1

Instrument 2

In Figure 3, without an external reference the instruments areunsynchronized. The histogram shows a variation of 4.2 radiansin their respective sampling times.

Figure 3: Internal Reference Jitter — distribution of jitter foracquisitions WITHOUT External Reference.

0

5

10

15

20

25

00.

61.

21.

82.

4 33.

64.

24.

85.

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In Figure 4, the instruments are synchronized, using a 10 MHzexternal reference: the difference in sampling time between themis very stable, as both sample at exactly the same time.

Figure 4: External Reference Jitter — distribution of jitter foracquisitions WITH an External Reference.

At 500 MS/s sample rate, for example, the time between twosamples is 2 ns, which is equivalent to a maximum jitter of 2 π. Inorder to ascertain whether the two instruments are trulysynchronized there must be a stable, or fixed, difference insampling time between them over several acquisitions.

External Reference Jitter

0

20

40

60

80

100

120

140

160

180

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The Trigger Comparator generates a positive pulse each time avalid trigger condition is met on the trigger signal‡. The pulse’sduration is constant, independent of trigger signal or condition.The characteristics of this trigger output signal ( Figs. 5–6 ):À Amplitude:

À ECL. 50 Ω, series-terminated (800 mV p-p typical)À LC564, LC584, DDA SERIES ONLY: ECL swing divided by

two (400 mV p-p typical) into 50 Ω load to ground

À Duration of Pulse Width:À Equal to time trigger signal is above/below the trigger levelÀ LC564, LC584, DDA SERIES ONLY: 1 ns typical

À Maximum Externally-applied Voltage: + 0 V, -2.5 V.

Figure 5: Trigger Output signal (ALL MODELS EXCEPT LC564, LC584, DDA).

‡ Edge Trigger only for all models except LC564AND LC584SERIES OSCILLOSCOPES, AND DDAS (DISK DRIVE ANALYZERS ).

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Figure 6: Trigger Output signal (LC564, LC584, DDA SERIES).

Figures 7–10 show a signal sent to the instrument on Channel 4,and the CKTRIG trigger output on Channel 3:

À ALL MODELS EXCEPT LC564, LC584, DDA SERIES: At thesame time there is a pulse output by the Trigger Comparatoron Channel 3 (Fig. 7) for each valid trigger condition andeach pulse of the trigger signal. This occurs even if noacquisition is performed with these triggers.

À LC564, LC584 AND DDA SERIES ONLY: At the same time onChannel 3 (Fig. 8) a pulse of typically 1 ns is generated eachtime a valid trigger condition is met on the trigger signal. Thisoccurs even if no acquisition is performed with these triggers.

Figure 7: Trigger Output on CH 4 generates a pulse on CH 3 each time avalid (Edge) trigger condition is met — here, on each positive slope (ALL

MODELS EXCEPT LC564, LC584, DDA SERIES).

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Figure 8: Trigger Output on CH 4 generates a pulse on CH 3 each time avalid Edge or SMART trigger condition is met — here, on each positive

slope (LC564, LC584, DDA ONLY).

Figures 9–10 show the same trigger signal and pulse, but withthe trigger condition set for triggering on a negative slope.

Figure 9: Trigger Output on CH 4 generates a pulse on CH 3 each time avalid (Edge) trigger condition is met — here, on each negative slope (ALL

MODELS EXCEPT LC564, LC584, DDA SERIES).

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Figure 10: Trigger Output on CH 4 generates a pulse on CH 3 each time avalid Edge or SMART trigger condition is met — here, on each negative

slope (LC564, LC584, DDA ONLY).

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Externally clocking at a fixed rate gives full phase-controlover the acquired signal. The sample rate, too, can be fine-tuned to the exact speed required. Note that for all modelsother than those in the LC564, LC584 AND DDA SERIES,calibration must be initiated for each external clock change.Input signal requirements (Figs. 11–12 ) are:

À Amplitude: 800 mV p-p typical; 1.25 V p–p minimum forguaranteed switching

À Frequency Range: 50 MHz to 500 MHzÀ LC564, LC584 AND DDA SERIES: DC to 500 MHz

À Sampling Uncertainty: ± 100 mV slew-rate signalÀ Minimum Slew Rate: < 1.25 ns/V

À LC564, LC584 AND DDA SERIES: 20 ns/V À Input impedance: 50 Ω ± 5 %À Maximum Input Voltage: ± 2.5 V

Figure 11: 50 MHz External Clock signal (ALL EXCEPT LC564, LC584, DDA).

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Figure 12: 50 MHz External Clock signal (LC564, LC584, DDA ONLY)

À Swept Clock: only a fixed-frequency clock can besupported; swept clock may cause offset errors of up to 10 %in the worst case.

Figures 13–14 show acquisitions using a 50 MHz external clock.

To enable the external clock, according to model and the menusavailable for that model, select either “RP” (Fig. 13), or“External” (Fig. 14), from the “TIMEBASE EXTERNAL” “SampleClock” menu. Or, by remote control, use the SAMPLE_CLOCKcommand (see page 21).

Figure 13: Acquisition of an external square signal using External Clock (ALLMODELS EXCEPT LC564, LC584, DDA).

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Figure 14: External Clock acquisition of a 1 kHz signal using 200 000 points at50 MHz. The displayed parameter units are in samples. (LC564, LC584, DDA

ONLY).

The following figure (Fig. 15) shows a similar acquisition andillustrates the recalibration menu. Calibration must be initiated foreach external clock change (ALL MODELS EXCEPT LC564,LC584 AND DDA).

Figure 15: Acquisition of a 100 kHz signal using 200k points with external clock(ALL MODELS EXCEPT LC564, LC584, DDA).

NNOOTT FFOORR LLCC556644,, LLCC558844,, DDDDAA This table shows a measurement on the same 1 V square signal at100 kHz with different external clock rates using 10 000 points. Foreach change of clock rate, at least one manual recalibration hasbeen performed. Gain and offset are extremely stable.

Clock rateMHz

AmplitudemV

MeanmV

rmsmV

50 998 7.5 500

100 999 9.1 500

150 1000 5.7 501

200 1000 7.5 501

300 998 7.9 501

400 997 7.5 499

500 1002 8.1 501

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À NNOOTT AAPPPPLLIICCAABBLLEE FFOORR LLCC556644,, LLCC558844 OORR DDDDAA SSEERRIIEESS:: When the external clockcharacteristics are changed, a manually performed calibration is required. This isdone either by altering sensitivity or, depending on the model, pressing the buttoncorresponding to the “RECALIBRATE” menu (see previous page).

À AALLLL MMOODDEELLSS:: In the “TIMEBASE” menu, the clock-source change can be slow.However, each press of a menu button is detected by the instrument during thewaiting time.

À AALLLL MMOODDEELLSS:: Any action that changes the timebase value WILL CAUSE THEINSTRUMENT TO REVERT TO THE INTERNAL CLOCK. Autosetup and timebase changes, fo rexample, CANNOT be used with external clock.

À AALLLL MMOODDEELLSS:: The minimum number of external clock cycles needed to perform anacquisition is NOT fixed. The instrument will require a number of cycles (typically 50)before it recognizes the external clock signal. The acquisition is halted only whenthe trigger conditions have been satisfied.

À NNOOTT AAPPPPLLIICCAABBLLEE FFOORR LLCC556644,, LLCC558844 OORR DDDDAA SSEERRIIEESS:: For calibration by RemoteControl, the *CAL? query is recommended.

Calibration cannot be performed with an external gated clock (Fig. 16). In order touse such a clock, the calibration must be done as follows:

1. Turn OFF autocalibration

2. Turn the external clock to a NON-GATED clock

3. Perform a calibration

4. Turn the external clock to a GATED clock and acquire data.

See, too the section on External Clock in the “Timebase Modes and Setup” chapter o fthe instrument Operator’s Manual.

Figure 16: Calibration CANNOT be performed with an external gated clock(ALL MODELS EXCEPT LC564, LC584, DDA). See final note, previous page.

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These remote control commands and queries are availableonly on instruments fitted with CKTRIG. For yourinstrument’s many other commands and queries, and anexplanation of its remote control, refer to the RemoteControl Manual.

$&48,6,7,21 5()(5(1&(B&/2&.5&/.Command/Query

'(6&5,37,21 REFERENCE_CLOCK selects the system clock source, allowing theinstrument to be phase-synchronized to an external reference clockinput.

&200$1'6<17$; Reference_CLocK <state>

<state> : = INT, EXT

48(5<6<17$; Reference_CLocK?

5(63216()250$7 Reference_CLocK <state>

$&48,6,7,21 6$03/(B&/2&.6&/.GCommand/Query

'(6&5,37,21 The SAMPLE_CLOCK command allows the user to control anexternal timebase. The user sets the number of data points thatwill be acquired when the instrument is using the external clock.When the optional suffix NUM is used with the query, theresponse will be returned in standard numeric format.

&200$1'6<17$; Sample_CLocK <state>[,<recordlength>][,<coupling>]

<state> : = INT, ECL, LV0, TTL, RPG<recordlength> : = 50, 100, 200, 500, 1K, 2K, 5K, 10K,

20K, 50K, 100K, 200K, 500K, 1M, 2M

Or, alternatively, in standard numeric format:

= 10e+3, 10.0e+3, 11e+3…, for example.<coupling> : = D1M or D50G

Note: The record length cannot be larger than the maximumavailable memory of the model being used. The instrument willadapt to the closest valid <recordlength>. See Appendix A of theinstrument Operator’s Manual for maximums.

48(5<6<17$; Sample_CLocK? [NUM]

G $9$,/$%,/,7< Not available on 9361C or 9362C Series oscilloscopes.

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Acquisition, 4, 5, 6Amplitude

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External Reference, 1, 2, 4Amplitude, 2enabling it, 3Frequency Range, 2Maximum Input Voltage, 2Offset, 2Sampling Uncertainty, 2

External vs Internal Reference, 6

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Frequency RangeExternal Reference, 2

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Internal vs External Reference, 5

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Minimum Slew RateExternal Clock, 13

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Phase-synchronization, 1, 2Pulse Width, 7, 8

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RECALIBRATE, 17Recalibration, 18Ref. Clock menu, 16REFERENCE_CLOCK, RCLK,

Command/Query, 3, 20Remote Control, 20

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clock, 1SAMPLE_CLOCK, SCLK,

Command/Query, 21Sampling time, 4, 6Sampling Uncertainty

External Clock, 13External Reference, 2

SPECIAL MODES, 3Swept Clock, 14Synchronization, 1, 2, 4, 6

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TIMEBASE, 3, 18Trigger Comparator, 1, 7, 8

Amplitude, 7Max. externally-applied

voltage, 7Pulse Width, 7, 8Trigger conditions, 8

8

UTILITIES, 3