DDA260 Disk Drive Analyzer Reference Manual - Edge Trigger

DDA-REF-E Rev D ISSUED: October 2000 9–1

9 Triggers and Their Operation

Edge Trigger

Selecting “Edge” and its menus (Fig. 9–1) causes the DDAto trigger whenever the selected signal source meets thetrigger conditions. The trigger source is defined by thetrigger level, coupling, slope or hold-off. Certain of thesebasic conditions applicable for SMART Trigger types arealso selected in “Edge.”

The symbol above is that of an edge trigger with positive slope —the highlighted edge — defined as the trigger condition.

Figure 9–1. Edge Trigger Menus.

Edge

Trigger on

Coupling

Slope Pos|Neg|Window

DC|AC|LFREJ|HFREJ|HF

1|2|3|4|Ext|Ext 5 |Line

Holdoff Off|Time|Events

9–2 ISSUED: October 2000 DDA-REF-E Rev D

Triggers and Their Operation

Trigger Source The trigger source may be:

Ø The acquisition channel signal (CH 1, CH 2, CH 3 or CH 4)conditioned for the overall voltage gain, coupling, andbandwidth.

Ø The line voltage that powers the DDA (LINE). This can beused to prov ide a stable display of signals synchronous withthe power line. Coupling and level are not relevant for thisselection.

Ø The signal applied to the EXT BNC connector (EXT). Thiscan be used to trigger the DDA within a range of ± 1.2 V onEXT and ± 6 V with EXT/5 as the trigger source.

Level Level defines the source voltage at which the trigger circuit willgenerate an event (a change in the input signal that satisfies thetrigger conditions). The selected trigger level is associated withthe chosen trigger source. Note that the trigger level is specifiedin volts and normally remains unchanged when the vertical gainor offset is modified.

The Amplitude and Range of the trigger level are limited asfollows:Ø ± 5 screen div isions with a channel as the trigger sourceØ ± 1.2 V with EXT as the trigger sourceØ ± 6 V with EXT/5 as the trigger sourceØ None with LINE as the trigger source (zero crossing is used).

Coupling This is the particular type of signal coupling at the input of thetrigger circuit. As with the trigger level, the coupling can beindependently selected for each source. Thus changing thetrigger source can change the coupling. The types of couplingable to be selected are:

Note: Once specified, Trigger Level and Coupling are theonly parameters that pass unchanged from trigger mode totrigger mode for each trigger source.


DDA

Ø DC: All the signal's frequency components are coupled tothe trigger circuit for high-frequency bursts or where the useof AC coupling would shift the effective trigger level.

Ø AC: The signal is capacitively coupled, DC levels arerejected and frequencies below 10 Hz attenuated.

Ø LF REJ: The signal is coupled v ia a capacitive high-passfilter network, DC is rejected and signal frequencies below100 MHz are attenuated. For stable triggering on medium-to high-frequency signals.

Ø HF REJ: Signals are DC-coupled to the trigger circuit and alow-pass filter network attenuates frequencies above50 kHz. For triggering on low frequencies.

Ø HF: To be used only when necessary for triggering on high-frequency repetitive signals > 300 MHz, with a maximumtrigger frequency of > 1 GHz. HF is automaticallyoverridden and set to AC when incompatible with othertrigger characteristics (and SMART Trigger types). Only oneslope available.

Slope Slope determines the direction of the trigger voltage transitionused for generating a particular trigger event. Like coupling, theselected slope is associated with the chosen trigger source.

Hold-off Without hold-off, the time between each successive triggerevent would be limited only by the input signal, the coupling, andthe DDA’s bandwidth.

However, sometimes a stable display of complex repetitivewaveforms can be achieved by placing a condition on this time.This is a hold-off, which can be expressed either as a period oftime or an event count. Hold-off disables the trigger circuit for agiven period of time or events (an event is the number ofoccasions on which the trigger condition is met) after the lasttrigger occurred. The trigger will again occur when the hold-offhas elapsed and the other specified conditions are met. Hold-offis used to obtain a stable trigger for repetitive, compositewaveforms. For example, if the number or duration of sub-signals is known, they can be disabled by choosing anappropriate hold-off value.



Hold-off by Time This is the selection of a minimum time between triggers(Fig. 9–2). A trigger is generated when the trigger condition ismet after the selected hold-off delay from the last trigger.The timing for the delay is initialized and started on each

trigger.

Figure 9–2. Edge Trigger with Hold-off by Time. The bold edges on the trigger source indicate apositive slope. The broken, upward-pointing arrows indicate potential triggers, which would occur

were other conditions met, while the two bold ones indicate where triggers actually occur when thehold-off time has been exceeded.

The symbol here indicates, as an example, apositive edge, trigger level of 0.008 V and a hold-offtime of 50 ns.

Hold-off time Hold-off time

Trigger Source: Positive Slope

Trigger can occur

Generated Trigger

TriggerEvent

TriggerEvent

TriggerEvent

Trigger initiateshold-off timer



DDA

Hold-off by Events Hold-off by events is initialized and started on each trigger(Fig. 9–3). A trigger is generated when the trigger condition is metafter the selected number of events from the last trigger. An event isdefined as the number of times the trigger condition is met after thelast trigger. For example, if the number selected is two, as it is inFigure 9–3, the trigger will occur on the third event. From 1 to99 999 999 events can be selected.

Figure 9–3. Edge Trigger with Hold-off by Events (in this example, by two events). The bold edgeson the trigger source indicate a positive slope. The broken, upward-pointing arrows indicate

potential triggers, while the bold ones show where triggers actually occur after the hold-off expires.

The symbol indicates a hold-off of 37 events.

Hold-off by 2 events Hold-off by 2 events


Trigger can occur

Generated Trigger

Event#1

Event#2

Event#2

Event#1

TriggerEvent

TriggerEvent

TriggerEvent


Triggerinitiateshold-offtimer



The Window Trigger (Fig. 9–4) allows the definition of awindow region whose boundaries extend above and belowthe selected trigger level. A trigger event occurs when thesignal leaves this window region in either direction and passesinto the upper or lower region. The next trigger will occur if andwhen the signal again passes into the window region. For atrigger to occur, the time that the signal spends within thewindow must be at least 0.5 ns.

Figure 9–4. Edge Window Trigger: trigger when the signal leaves the window region.

The symbol indicates the trigger level and the range of the window region.

Window TriggerW

IND

OW

RE

GIO

N

Trigger Level

Triggers

Time

Lower Region

Upper Region


DDA

SMART TriggerSMART Trigger allows the setting of additional qualificationsbefore a trigger is generated. Types include triggers adaptedfor glitches, intervals, abnormal signals, TV signals, state- oredge-qualified events, dropouts, patterns, “runts” and slewrate.

Glitch Trigger In general, a glitch is a pulse much faster than the observedwaveform. Glitch Trigger (Fig. 9–5) is used to capture narrow pulsesless than or equal to, or greater than or equal to, a given time limit.

The symbol above indicates, as an example, a pulse width of 10 ns.Figure 9–5. Glitch Trigger Menus.

Glitch

Trigger on

Coupling

At end of Neg|Pospulse

DC|AC|LFREJ|HFREJ

1|2|3|4|Ext|Ext 5

Width: lessthan or equal

toOff|Time

Width:greater thanor equal to

Off|Time



GlitchWidth

Generated Trigger

GlitchWidth

WidthSelected

Trigger Source

Trigger can occur

WidthSelected

Glitch Applications Digital electronics circuits normally use an internal clock, and fortesting purposes, a glitch can be defined as any pulse of widthsmaller than the clock- or half-period. Glitch Trigger has a broadrange of applications in digital and analog electronic development,ATE, EMI, telecommunications, and magnetic media studies.

This Glitch Trigger selects a maximum pulse width (Fig. 9–6). Itis generated on the selected edge when the pulse width is lessthan or equal to the selected width. The timing for the width isinitialized and restarted on the opposite slope to that selected.Glitches as short as 600 ps can be triggered on, and widths of600 ps–20 s selected. On the other models, widths of between2.5 ns and 20 s can be selected, but typically triggering willoccur on glitches 1 ns wide.

Figure 9–6. Glitch Trigger: here on a pulse width less than or equalto the width selected. The broken, upward arrow indicates a

potential trigger, while the bold one shows where the actual triggeroccurs.

Pulse Smaller thanSelected Pulse Width


DDA

Exclusion Trigger Selecting “Glitch” and setting width conditions can also enablethe exclusion of events that either fall within, or outside of, aselected width range. This is an exclusion trigger (Fig. 9–7).When it is decided to exclude from triggering all those eventswithin a particular range, only pulses outside — less-than-or-equal-to or greater-than-or-equal-to — this range will generate atrigger event. Alternatively, it may be decided to trigger only onthose pulses in the range itself and exclude all those outside it.The timing for the width is initialized and restarted on the slopeopposite to the selected edge. Widths of the same values as forGlitch Trigger can be selected (see previous page).

Figure 9–7. Exclusion Trigger. In this example, only pulses outsidethe boundaries of the width range, those of ≤ 25.0 ns or ≥ 27.5 nsin length, will be captured. Note the “OR” in the “width ≥” menu,which changes to “&” when triggering only within the range.

Exclusion Applications Exclusion Triggers allow a signal’s normal width or period to bespecified, with the DDFA instructed to ignore the normallyshaped signals and trigger only on abnormal ones. Circuitfailures, for instance, can be looked for all the time.



Interval Trigger Whereas Glitch Trigger performs over the width of a pulse,Interval Trigger (Fig. 9–8) performs over the width of aninterval. An interval corresponds to a the signal duration (theperiod) separating two consecutive edges of the same polarity:positive to positive edge; negative to negative edge. IntervalTrigger is used to capture intervals that are inferior to or exceedinga given time limit. In addition, a width range can be defined tocapture any interval that is comprised within or outside the specifiedrange — an Exclusion Trigger by Interval.

Figure 9–8. Interval Trigger Menus.

Interval Applications Interval Trigger is helpful for determining missing cycles ortransitions and for ignoring unwanted signal reflections.

Interval

Trigger on

Coupling

Between Neg|Posedges

DC|AC|LFREJ|HFREJ

1|2|3|4|Ext|Ext5

Interval:less than or

equal toOff|Time

Interval:greater thanor equal to

Off|Time


DDA

Interval Smaller For this Interval Trigger, generated on a time interval smaller thanthe one selected, a maximum interval between two like edges of thesame slope — positive, for example — is chosen (Fig. 9–9). Thetrigger is generated on the second (positive) edge if it occurs withinthe selected interval. The timing for the interval is initialized andrestarted whenever the selected edge occurs. Intervals of between2 ns and 20 s can be selected.

Figure 9–9. Interval Trigger that triggers when the interval width issmaller than the selected interval. The broken, upward-pointing

arrow indicates a potential trigger, while the bold one showswhere the actual trigger occurs — on the positive edge within the

selected interval.

The symbol indicates a positive slopeand interval of ≤ 1.99 ms selected.

Generated Trigger

SelectedInterval


Trigger can occur

SelectedInterval

Interval Width IntervalWidth



Interval Larger For this Interval Trigger, generated on an interval larger than theone selected, a minimum interval between two edges of thesame slope is selected (Fig. 9–10). The trigger is generated onthe second edge if it occurs after the selected interval. Thetiming for the interval is initialized and restarted whenever theselected edge occurs. Intervals of between 2 ns and 20 s can be

selected.Figure 9–10. Interval Trigger that triggers when the interval widthis larger than the selected interval. The broken, upward-pointing

arrow indicates a potential trigger, while the bold one showswhere the actual trigger occurs — on the positive edge after the

selected interval.

Interval Width

Generated Trigger

SelectedInterval


Trigger can occur

SelectedInterval

IntervalWidth


DDA

The symbol indicates a positive slope and interval of ≥ 258 nsselected.



Interval Between Range This Interval Trigger is generated whenever an interval betweentwo edges of the same slope falls within a selected range (Fig.9–11). The timing for the interval is initialized and restartedwhenever the selected edge occurs. Intervals of between 2 nsand 20 s can be selected.

Figure 9–11. Interval Trigger that triggers when the interval fallswithin the selected range: T1 = the range’s lower time limit; T2 itsupper limit. The broken, upward-pointing arrow indicates apotential trigger, while the bold one indicates where the actualtrigger occurs — on the positive edge within the selected range.

The symbol indicates a positiveslope, range limits of ≥ 10.0 ns and≤ 5.4 µs, selected.

Interval Width

Generated Trigger

Trigger can occur


0 0T1 T1T2 T2

RangeRange

IntervalWidth


DDA

Interval Outside Range This Interval Trigger is generated whenever an interval betweentwo edges of the same slope falls outside a selected range (Fig.9–12). The trigger is generated on the second edge if it occursafter the selected interval range. The timing for the interval isinitialized and restarted whenever the selected edge occurs.Intervals of between 2 ns and 20 s can be selected.

Figure 9–12. Interval Trigger that triggers when the interval fallsoutside the selected range: T1 = the range’s lower time limit; T2 its

upper limit. The broken, upward-pointing arrow indicates apotential trigger, while the bold one shows where the actual trigger

occurs, on the positive edge outside the selected range.

The symbol indicates a positive slope,and range limits of ≤ 10.0 ns and ≥347.5 ns selected. “OR” means thatintervals above or below the range havebeen targeted.

Interval Width

Generated Trigger

Trigger can occur


0 0T1 T1T2 T2

RangeRange

IntervalWidth



Pattern Trigger Pattern Trigger (Fig. 9–13) enables triggering on a logicalcombination of the five inputs CH 1, CH 2, CH 3, CH 4 and EXT.This combination, called a pattern, is defined as the logical AND oftrigger states. A trigger state is either high or low: high when atrigger source is greater than the trigger level, or threshold, and lowwhen less than it (Fig. 9–14). For example, a pattern could bedefined as present when the trigger state for CH 1 is high, CH 2 islow, and EXT is irrelevant (X or don’t care). If any of theseconditions are not met, the pattern state is considered absent. Hold-off limits from 2 ns to 20 s, or from 1 to 99 999 999 events, can beselected.

Figure 9–13. Pattern Trigger Menus.

Pattern

Trigger on

Patternwith

Coupling DC|AC|LFREJ|HFREJ

1|2|3|4|Ext

Exiting | Entering

Level L|H|X|(Level value)

Off|Time|EvtsHoldoff


DDA

Pattern Applications Pattern Trigger can be used in digital design for the testing ofcomplex logic inputs or data transmission buses.

Figure 9–14. Pattern Trigger: triggers when all pattern conditionsare met. Bold, upward-pointing arrows show where triggers occur.

Information summarizing the pattern set up is displayed.

CH 1

Generated Trigger (Pattern Entering)

Pattern 1H*2L

Threshold

CH 2

Generated Trigger (Pattern Exiting)

Threshold

High

High

Low

Low



More About Pattern Trigger Once the pattern is defined, one of two transitions can be usedto generate the trigger. When the pattern begins, called enteringthe pattern, a trigger can be generated. Alternatively, a triggercan be generated when the pattern ends, exiting the pattern.

With pattern triggering, as in single source, either of thesequalifications can be selected: Hold-off for 2 ns–20 s, or Hold-off for1 to 99 999 999 events.

Set to Pattern Trigger, the DDA always checks the logic AND of thedefined input logic states. However, with the help of de Morgan'stheorem, the pattern becomes far more generalized.

Consider the important example of the Bi-level or Window PatternTrigger. Bi-level implies the expectation of a single-shot signal onwhich the amplitude will go in either direction outside a knownrange. To set up a Bi-level Pattern trigger, connect the signal to twoinputs: Channels 1 and 2 or any other pair that can be triggered on.For example, the threshold of CH 1 could be set to +100 mV andthat of CH 2 at -200 mV. The Bi-level Trigger will occur if the DDAtriggers on CH 1 for any pulse greater than +100 mV, or on CH 2 forany pulse less than –200 mV. For improved precision, the gains ofthe two channels should be at the same setting.

In Boolean notation we can write:

Trigger CH 1 CH 2= + ,

i.e., trigger when entering the pattern CH 1 = high OR CH 2 = low.

By de Morgan's theorem this is equivalent to:

Trigger CH 1 CH 2= ⋅ ,

i.e., trigger when exiting the pattern CH 1 = low AND CH 2 =high. This configuration can be easily programmed.

The possibility of setting the threshold indiv idually for eachchannel extends this method so that it becomes a more generalWindow Trigger: in order to trigger the input pulse amplitudemust lie within or outside a given arbitrary window.

Pattern Trigger has been designed to allow a choice of the triggerpoint. By choosing 1L*2H entering, the trigger will occur at themoment the pattern 1L*2H becomes true.


DDA

Qualified Triggers In the case of Qualified Triggers (Fig. 9–15), a signal’s transitionabove or below a given level — its validation — serves as anenabling, or qualifying, condition for a second signal that is thesource of the trigger.

Two Qualified Triggers are available: State-Qualified, where theamplitude of the first signal must remain in the desired stateuntil the trigger occurs, and Edge-Qualified, for which thevalidation is sufficient and no additional requirement is placedon the first signal (for the separate, Qualified First Trigger, seepage 9–1).

A Qualified Trigger can occur immediately after the validation orwithin a set time after it. Or it can occur following apredetermined time delay or number of potential trigger events.The time delay or trigger count is restarted with every validation.

Figure 9–15. State- and Edge-Qualified Trigger Menus.

Qualified

By

Trigger on

After

Edge|State qualifier

Has gone Above|Belowvalue

WithinWait Off|Time <| Time> | Evts

1|2|3|4|Ext|Ext5

1|2|3|4|Ext|Ext5

Qualified

By

Trigger on

Only after 1|2|3|4|Ext|Ext5

1|2|3|4|Ext|Ext5


Goes andstays

Above|Belowvalue

Off|Time <| Time> | EvtsWithinWait



Qualified Triggers offer the choice of generating a trigger eitherwhen a selected pattern is present or absent. As with PatternTrigger, the pattern is defined as a logical AND combination oftrigger states that are either high or low: high when a triggersource is greater than the selected trigger level, and low when itis less than. For example, a pattern might be defined as presentwhen the trigger states for Channels 1 and 2 are high and EXT islow. If any of these conditions is not met, the pattern state isconsidered absent.

Qualified Triggers allow an additional qualification once theselected pattern state occurs. For example: “wait for 10 ns up to20 s, trigger on CH 1 to the 99 999 999th event”. The pattern isused to qualify the trigger without actually generating it.Triggering will occur when another signal, the trigger source,meets its trigger condition while the pattern is present. Thetrigger source itself is not allowed in the pattern.

Qualified Applications Typical applications can be found wherever time v iolationsoccur, such as in microprocessor debugging ortelecommunications.

State-Qualified with Wait State-Qualified Trigger with Wait (Fig. 9–16) is determined bythe parameters of Time or the number of Events:

Ø Time determines a delay from the start of the desiredpattern. After the delay (timeout) and while the pattern ispresent, a trigger can occur. The timing for the delay isrestarted when the selected pattern begins.

Ø Events determines a minimum number of events of thetrigger source. An event is generated when a trigger sourcemeets its trigger conditions. On the selected event of thetrigger source and while the pattern is present, a trigger canoccur. The count is initialized and started whenever theselected pattern begins, and continues while the patternremains. When the selected count is reached, the triggeroccurs.


DDA

This symbol is that for a State-Qualified-with-time-Wait trigger:positive slope, 2 ns delay, “goes and stays Above” -24 mV.



Figure 9–16. State-Qualified by Wait: Trigger after timeout. The broken, upward-pointing arrowsindicate potential triggers, while the bold arrows show where the actual triggers occurs.

As the above figure illustrates, a trigger is generated on a risingedge whenever the pattern is asserted (pattern present) and thewait timeout has expired. The timeout is activated or disabledonce the pattern is asserted or absent.

The symbol shown here is that of an Edge-Qualified-with-event Waittrigger on CH 2 (described next page): positive slope, wait of 109

events, level of 2.50 V, and pattern present as indicated.

Generated TriggerWait


Trigger can occur

Qualifier: Pattern Present

Wait


DDA

Edge-Qualified with Wait Like its State-Qualified equivalent, Edge-Qualified with Wait(Fig. 9–17) is conditioned by either Time or Events:Ø Time determines a delay from the start of the desired

pattern. After the delay (timeout) and before the end of thepattern, a trigger can occur. The timing for the delay isrestarted when the selected pattern begins.

Ø Events determines a minimum number of events for thetrigger source. An event is generated when a trigger sourcemeets its trigger conditions. A trigger can occur on theselected event of the trigger source and before the end ofthe pattern. The count is initialized and started whenever theselected pattern begins. It continues while the patternremains. When the selected count is reached, the triggeroccurs.

Figure 9–17. Edge-Qualified by Wait: Trigger after timeout. The broken,upward-pointing arrows indicate potential triggers, while the bold

ones show where the actual trigger occurs.

SelectedTime

SelectedTime


Qualifier: Pattern Present

Trigger can occur

Generated Trigger



Qualified First Trigger (Fig. 9–18) is similar to the QualifiedTriggers and presents exactly the same menus. Qualified First isintended to be used exclusively in Sequence Mode to speed upthe trigger rate. With Qualified First, a single valid trigger issufficient to acquire a full sequence. Other than in SequenceMode, Qualified First is identical to the Qualified Triggers.

Figure 9–18. Qualified First Trigger Menus.

Applications In Data Storage, the index pulse can be defined as the qualifiersignal, and the servo gate signal as the trigger source.

Qual First

By

Trigger on

After


Has gone Above|Belowvalue

WithinWait Off|Time <| Time> | Evts

1|2|3|4|Ext|Ext5

1|2|3|4|Ext|Ext5

Qualified First Trigger


DDA

Figure 9–19. Comparing Qualified (top) and Qualified First (bottom) Triggers. Whereas the (Edge-)Qualified Trigger requires that each of the segments be “qualified” by a valid condition in Sequence

Mode, Qualified First Trigger needs only a single valid condition to qualify a full sequence ofsegments. Note that the inter-segment deadtime (DT) is much shorter with Qualified First, which is

used only in Sequence Mode.

Qualified First Trigger symbol.

DT

Qualifier

Segment 1DT

Trigger

Segment 2 Segment N

DT

Qualifier

Segment 1

Trigger

Segment 2 Segment NDT

(Edge-)Qualified Trigger

Qualified First Trigger



TV Trigger A special kind of Edge-Qualified Trigger, TV Trigger (Fig. 9–20)allows stable triggering on standard or user-defined compositev ideo signals, on a specific line of a given field. TV Trigger canbe used on PAL, SECAM or NTSC systems.

A composite video signal on the trigger input is analyzed to providea signal for the beginning of the chosen field — “any”, “odd” or“even” — and for a signal at the beginning of each line. The fieldsignal provides the starting transition, and the beginnings of linepulses are counted to allow the final trigger on the chosen line. Eachfield, the number of fields, the field rate, interlace factor, andnumber of lines per picture must be specified — although there arestandard settings for the most common types of TV signals. TVTrigger can also function in a simple any-line mode.

Figure 9–20. TV Trigger Menus.

TV

TV signal on

# of fields

TV type Standard | Custom

1|2|4|8

1|2|3|4|Ext|Ext5

as: 625/50/2:1| 525/60/2:1(Standard)

as: Line#|Hz|Interlacing#:#(Custom)

Trigger on Line# | Field# |any


DDA

The TV Trigger symbol shown here indicates a trigger on Line 338 ofthe second of eight fields of a PAL/SECAM signal on CH 1. The “25” inparentheses is the number of the line selected in Field 1.

Notes for TV Trigger

Ø Because most TV systems have more than two fields, the enhanced field-countingcapability (FIELDLOCK) allows the DDA to trigger consistently on a chosen linewithin a chosen field of the signal. The field-numbering system is relative, in thatthe DDA cannot distinguish between lines 1, 3, 5, and 7 (or 2, 4, 6, and 8) in anabsolute way.

Ø For each of the characteristics the following remarks apply:

Ø 625/50/2:1 (PAL and SECAM systems)

This setting should be used for most of the standard 50-field signals. Thelines may be selected in the range 1 to 626 where line 626 is identical to line1.

Number of fields: “4” is most useful for color PAL signals; “8” for SECAMsignals.

Ø 525/60/2:1 (NTSC systems)

This setting should be used for standard 60-field NTSC signals. The lines canbe selected in the range 1 to 1051, where line 1051 is identical to line 1.

Number of fields: “4” is most useful for US-type NTSC systems.

Ø ?/50/?, ?/60/?

In order to allow maximum flexibility, no line-counting convention is used.The line count should be thought of as a line-synchronizing pulse count. Itincludes the transitions of the equalizing pulses. For certain extreme cases,the field transition recognition will no longer work, and only the “any line”mode will be available.

Ø The enhanced field-counting capability cannot be used for RIS acquisitions.

Ø Composite video signals must have negative-going synch to be decoded correctly.



Dropout Trigger Dropout Trigger (Fig. 9–21) prov ides triggering whenever thesignal disappears for a set period of time. The trigger isgenerated at the end of the time-out period following the “last”trigger-source transition, as shown in the figure on the next page(Fig. 9–23). Time-outs of between 2 ns and 20 s can beselected.

Figure 9–21. Dropout Trigger Menus.

Dropout Applications Dropout Trigger is useful for detecting interruptions in datastreams such as network hang-ups and microprocessor crashes.A typical application is on the last ‘normal’ interval of a signalthat has disappeared completely. This is essentially a single-shot application, usually with a pre-trigger delay. RIS acquisitionis not useful here because the timing of the trigger timeout isinsufficiently correlated to the input channel signals.

Dropout

Trigger aftertimeout if no edge

occurs on

With slope

Within Time

Positive|Negative

1|2|3|4|Ext|Ext5


DDA

Figure 9–22. Dropout Trigger: occurs when the time-out has expired. The bold, upward-pointingarrows show where the trigger occurs.

This Dropout Trigger symbol indicates a a waittime-out of 25 ns.

Generated Trigger

Trigger Source

Trigger can occurWait

Time-outWait

Time-out



Runt

Trigger on

Coupling

With Level: upper level |lower level

DC|AC|LFREJ|HFREJ

1|2|3|4|Ext|Ext5

Width: runt <= | runt >=

Edge: Negative | Positive

The Runt Trigger (Fig. 9–23) is programmed to occur when apulse crosses a first threshold line and fails to cross a secondthreshold line before re-crossing the first (Fig. 9–24). Boththresholds can be selected within a range of 600 ps–20 s. Otherdefining conditions for this trigger are the edge (triggers on theopposite slope to that selected) and the runt width.

Figure 9–23. Runt Trigger Menus.

Runt Applications Runt Trigger is particularly helpful for detecting meta-stableconditions in digital design.

Runt Trigger


DDA

Figure 9–24. Runt Trigger: triggers when a pulse crosses the first threshold but not the second beforere-crossing the first — marked by the bold, upward-pointing arrows.

The symbol indicates a positive edge (“Neg” was selected to obtainthis), the difference between the two threshold levels (“veto”), and

the runt width.

Trigger Source

Generated Trigger (Positive Slope)

Generated Trigger (Negative Slope)

Upper Threshold Level

Lower Threshold Level



Slew Rate Trigger (Fig. 9–25) activates a trigger when the risingor falling edge of a pulse crosses two threshold levels: an upperand a lower level (Fig. 9–26). The pulse edge must cross thethresholds either faster or slower than a selected period of time.Both thresholds are able to be selected within a range of600 ps–20 s.

Figure 9–25. Slew Rate Trigger Menus.

Applications Slew Rate Trigger is useful for measuring risetime or falltime indigital design, minimizing reflections.

Slew Rate

Trigger on

Coupling

With dV: upper level |lowerlevel

DC|AC|LFREJ|HFREJ

1|2|3|4|Ext|Ext5

dT: dT <= | dT >=

Slope: Negative | Positive

Slew Rate Trigger


DDA

Figure 9–26. Slew Rate Trigger: occurs when a rising or falling edge crosses two thresholds (dV)outside a selected time range (dT), marked by the bold, upward-pointing arrow.

The Slew Rate symbol is the same as the Edge Trigger symbol,but indicates lower (0.556 V) and upper (188 m) threshold levels,

and a time range — here, 73.6 mV/ns.

Trigger Source

Generated Trigger

UpperThreshold Level

Lower ThresholdLevel

dT

dV

dT dT dT



DISK TriggersDISK Triggers are the DDA’s drive-specific triggers.

Sector Pulse Trigger Sector Pulse Trigger (Fig. 9–27) triggers on the specified edge (Posor Neg) of a specified sector after an Index (Fig. 9–28). Thethresholds for Index and Sector pulse are set to 1.5 V.

Figure 9–27. Sector Pulse Trigger menus.

SectorPulse

Trigger on

Sector Pulse

Index

Polarity: Neg|Pos

1|2|3|4|Ext5

Sector # after Index

1|2|3|4|Ext5

Polarity: Neg|Pos


DDA

Figure 9–28. Servo Gate Trigger: occurs (bold, upward-pointing arrow) on the specified edge (Pos or Neg)of the nth sector.

Generated Trigger

Index

Sector Pulse nth sector after Index



Read Gate Trigger The Read Gate Trigger (Fig. 9–29) triggers on the specifiededge (Pos or Neg) of a pulse that is longer than a specified time(Fig. 9–30). The minimum pulse width is specified so that theRead Gate Trigger does not trigger on other narrower pulsessuch as ID fields. The thresholds for Read Gate Trigger are set to1.5 V.

Figure 9–29. Read Gate Trigger Menus.

Read Gate

Read Gate

Read Gate

Width > Time

Polarity: Neg|Pos

1|2|3|4


DDA

Figure 9–30. Read Gate Trigger: occurs (bold, upward-pointing arrow) on the trailing edge of a Read Gatewider than a specified width. The polarity of the Read Gate signal can also be specified.

Generated Trigger

Trigger Source

WidthWidth



Servo Gate Trigger The Servo Gate Trigger (Fig. 9–31) triggers periodically byskipping a specified number of Servo Gates after each trigger(Fig. 9–32). The initial trigger occurs at the specified ServoGate after an Index pulse. The thresholds for Index and ServoGate are set to 1.5 V.

Figure 9–31. Servo Gate Trigger Menus.

Servo Gate

Trigger on

Secotr Pulse

Index

Polarity: Neg|Pos

1|2|3|4|Ext5

After Index Wait

1|2|3|4|Ext5

Polarity: Neg|Pos

Then Skip #


DDA

Figure 9–32. Servo Gate Trigger: occurs periodically (bold, upward-pointing arrows) on the specified edge(Pos or Neg) of a Servo Gate by skipping a specified number of Servo Gates. The first trigger occurs at thespecified Servo Gate after Index.

Generated Trigger

Index

Servo Gate

Wait m Servo Gates

Skip n Servo Gates Skip n Servo Gates



PES Window Trigger The PES Window Trigger (Fig. 9–33) is similar to the EdgeWindow Trigger (Fig. 9–34) but allows the trigger to be furtherqualified by the state of Servo Gate. The trigger occurswhenever the PES signal leaves the specified window region.

Figure 9–33. PES Window Trigger Menus.

PESWindow

Window

PES

Servo Gate

within

1|2|3|4

PES Offset

1|2|3|4|Ext|Ext5

Polarity: Neg|Pos


DDA

Figure 9–34. PES Window Trigger: while Servo Gate remains true, triggers whenever the PES signalleaves the window region. The broken, upward-pointing arrows indicate potential triggers, which would

occur were other conditions met, while the bold ones indicate where triggers actually occur.

# # #

Generated Trigger

PES Signal

PES Offset

Window

Servo Gate



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DDA260 Disk Drive Analyzer Reference Manual - Edge Trigger

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