24 Triggers

24.1 Trigger Properties

TODO: Replace glscopeclient figures

The Setup / Trigger menu opens the trigger properties dialog (Fig. 24.1).

The Trigger Type box allows the type of trigger to be chosen. The list of available triggers depends on the instrument model and installed software options.

The Trigger Offset field specifies the time from the emph{start} of the waveform to the trigger point. Positive values move the trigger later into the waveform, negative values introduce a delay between the trigger and the start of the waveform. [1]

[1]

This is a different convention than most oscilloscopes, which typically measure the trigger position from the midpoint of the waveform. Since ngscopeclient decouples the acquisition length from the UI zoom setting, measuring from the midpoint makes little sense as there are no obvious visual cues to the midpoint’s location.

Fig. 24.1 Trigger properties dialog

The remaining settings in the trigger properties dialog depend on the specific trigger type chosen.

24.2 Serial Pattern Triggers

All serial pattern triggers take one or two pattern fields, a radix, and a condition.

For conditions like between or not between both patterns are used, and no wildcards are allowed. For other conditions, only the first pattern is used.

Patterns may be specified as ASCII text, hex, or binary. Don't care nibbles/bits may be specified in hex/binary patterns as X, for example 3fx8 or 1100010xxx1.

24.3 Dropout

Triggers when a signal stops toggling for a specified amount of time.

24.3.1 Inputs

Signal name	Type	Description
din	Analog or digital	Input signal

24.3.2 Parameters

Parameter name	Type	Description
Edge	Enum	Specifies the polarity of edge to look for (rising or falling)
Dropout Time	Int	Dropout time needed to trigger
Level	Float	Voltage threshold
Reset Mode	Enum	Specifies whether to reset the timer on the opposite edge

24.4 Edge

Triggers on edges in the signal.

Edge types rising and falling are self-explanatory. Any triggers on either rising or falling edges. Alternating is a unique trigger mode only found on certain Agilent/Keysight oscilloscopes, which alternates each waveform between rising and falling edge triggers.

24.4.1 Inputs

Signal name	Type	Description
din	Analog or digital	Input signal

24.4.2 Parameters

Parameter name	Type	Description
Edge	Enum	Specifies the polarity of edge to look for
Level	Float	Voltage threshold

24.5 Glitch

TODO: This is supported on at least LeCroy hardware, but it’s not clear how it differs from pulse width.

24.6 Pulse Width

Triggers when a high or low pulse meeting specified width criteria is seen.

Signal name	Type	Description
din	Analog or digital	Input signal

24.6.1 Parameters

Parameter name	Type	Description
Condition	Enum	Match condition (greater, less, between, or not between)
Edge	Enum	Specifies the polarity of edge to look for
Level	Float	Voltage threshold
Lower Bound	Int	Lower width threshold
Upper Bound	Int	Upper width threshold

24.7 Runt

Triggers when a pulse of specified width crosses one threshold, but not a second.

Signal name	Type	Description
din	Analog	Input signal

24.7.1 Parameters

Parameter name	Type	Description
Condition	Enum	Match condition (greater, less, between, or not between)
Edge Slope	Enum	Specifies the polarity of edge to look for
Lower Interval	Int	Lower width threshold
Lower Level	Float	Lower voltage threshold
Upper Interval	Int	Upper width threshold
Upper Level	Float	Upper voltage threshold

24.8 Slew Rate

Triggers when an edge is faster or slower than a specified rate.

Signal name	Type	Description
din	Analog	Input signal

24.8.1 Parameters

Parameter name	Type	Description
Condition	Enum	Match condition (greater, less, between, or not between)
Edge Slope	Enum	Specifies the polarity of edge to look for
Lower Interval	Int	Lower width threshold
Lower Level	Float	Lower voltage threshold
Upper Interval	Int	Upper width threshold
Upper Level	Float	Upper voltage threshold

24.9 UART

Triggers when a byte or byte sequence is seen on a UART.

24.9.1 Inputs

Signal name	Type	Description
din	Analog or digital	Input signal

24.9.2 Parameters

Parameter name	Type	Description
Bit Rate	Int	Baud rate
Condition	Enum	Match condition
Level	Float	Voltage threshold
Parity Mode	Enum	Odd, even, or no parity
Pattern	String	First match pattern
Pattern 2	String	Second match pattern
Polarity	Enum	Idle high (normal UART) or idle low (RS232)
Radix	Enum	Radix for the patterns
Stop Bits	Float	Number of stop bits
Trigger Type	Enum	Match data pattern or parity error

24.10 Window

Triggers when a signal goes above or below specified thresholds.

The available configuration settings for this trigger vary from instrument to instrument.

Signal name	Type	Description
din	Analog	Input signal

24.10.1 Parameters

Parameter name	Type	Description
Condition	Enum	Specifies whether to trigger on entry or exit from the window, and whether to trigger immediately or after a time limit.
Edge	Enum	Specifies which edge of the window to trigger on
Lower Level	Float	Lower voltage threshold
Upper Level	Float	Upper voltage threshold