Patent Publication Number: US-9846184-B2

Title: Combinatorial mask triggering in time or frequency domain

Description:
BACKGROUND 
     Embodiments of the present invention relate to mask triggering, and more particularly, to combinatorial mask triggering in the time or frequency domain on a test and measurement instrument. 
     Modern test and measurement instruments, such as high-speed digital oscilloscopes, include acquisition systems that capture measurement data pertaining to incoming electrical signals under test. Different kinds of criteria can be used to trigger an acquisition of data on the test and measurement instrument. For example, triggering can be based on a “mask region” defined within the drawing plane of a display device. Trigger logic can detect excursions of trace components represented by pixels drawn on the display within the mask region, and in response, cause a mask failure and/or trigger event to occur. 
     In a conventional frequency mask triggering system, a spectrum acquisition process is “free-running,” or in other words, as soon as the system is ready, acquisition data is acquired and processed to generate a spectrum. This spectrum is then rasterized into an image plane. As the individual spectrum traces or frequency components are rasterized, they are tested against the frequency mask. If the trace fails the mask criteria (e.g., an excursion through the mask region occurs), a trigger is generated, and digital data is acquired and stored in a memory. 
     In a conventional time domain triggering system, triggering can occur based on a variety of criteria. For example, acquired data can be tested against one or more “visual trigger zones” and if zone criteria are met, then the acquired waveform is processed further. If the zone criteria are not met, the waveform is discarded. 
     What is missing in conventional approaches is the element of time relative to special considerations. More specifically, while signals and relationships between components of signals can be expressed in terms of space and/or time, the conventional triggering methods lack the ability to build associations and trigger criteria around spatial aspects in combination with time-related aspects of the signal under test. 
     Moreover, while multiple mask regions or visual trigger zones are known, there remains a need for multiple region mask triggering and/or density triggering in both time and frequency domain acquisitions. Accordingly, a need remains for combinatorial mask triggering involving multiple trigger mask regions, along with trigger criteria involving logical, spatial and/or timing relationships between the mask regions, so that more sophisticated triggering modes can be supported. Embodiments of the invention address these and other limitations in the prior art. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  illustrates an example test and measurement instrument including combinatorial mask triggering logic in accordance with embodiments of the present invention. 
         FIG. 2  illustrates a flow diagram showing a technique for combinatorial mask triggering in terms of space and time in accordance with embodiments of the present invention. 
         FIGS. 3A-3B  illustrate a trace and an associated flow diagram, respectively, in accordance with an embodiment of the present invention. 
         FIGS. 4A-4C  illustrate a first trace, a second trace, and an associated flow diagram, respectively, in accordance with another embodiment of the present invention. 
         FIGS. 5A-5B  illustrate a trace and an associated flow diagram, respectively, in accordance with yet another embodiment of the present invention. 
         FIGS. 6A-6B  illustrate a trace and an associated flow diagram, respectively, in accordance with still another embodiment of the present invention. 
         FIGS. 7A-7D  illustrate a first trace, a second trace, an associated flow diagram relative to the frequency domain, and an associated flow diagram relative to the time domain, respectively, in accordance with another embodiment of the present invention. 
     
    
    
     The foregoing and other features and advantages of the inventive concepts will become more readily apparent from the following detailed description of the example embodiments, which proceeds with reference to the accompanying drawings. 
     DETAILED DESCRIPTION 
     Reference will now be made in detail to embodiments of the present invention, examples of which are illustrated in the accompanying drawings. In the following detailed description, numerous specific details are set forth to enable a thorough understanding of the inventive concepts. It should be understood, however, that persons having ordinary skill in the art may practice the inventive concepts without these specific details. In other instances, well-known methods, procedures, components, circuits, and networks have not been described in detail so as not to unnecessarily obscure aspects of the embodiments. 
     It will be understood that, although the terms first, second, etc. may be used herein to describe various elements, these elements should not be limited by these terms. These terms are only used to distinguish one element from another. For example, a first trigger mask could be termed a second trigger mask, and, similarly, a second trigger mask could be termed a first trigger mask, without departing from the scope of the inventive concept. 
     The terminology used in the description of the various embodiments herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the inventive concepts. As used in the description and the appended claims, the singular forms “a”, “an” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will also be understood that the term “and/or” as used herein refers to and encompasses any and all possible combinations of one or more of the associated listed items. It will be further understood that the terms “comprises” and/or “comprising,” when used in this specification, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof. The components and features of the drawings are not necessarily drawn to scale. 
       FIG. 1  illustrates an example test and measurement instrument  105  including combinatorial logic  170  in accordance with embodiments of the present invention. The test and measurement instrument  105  can be an oscilloscope, a logic analyzer, a spectrum analyzer, a mixed-domain oscilloscope, a network analyzer, or the like. Generally, for the sake of consistency and explanation, the test and measurement instrument  105  is referred to herein as an oscilloscope. 
     The oscilloscope  105  can include an input section  135 , which receives an input electrical signal under test  140 . The input section  135  can include acquisition circuitry, digitizers, amplifiers, converters, or the like, and can be connected to a memory  115  via line  130 . The memory  115  can store one or more acquisition records related to the input signal  140  in response to a trigger event. The memory  115  can include a memory controller  120 , which controls the writing and reading of digitized data to and from the memory  115 . The memory  115  can be dynamic memory, static memory, read-only memory, random-access memory, or any other suitable variety of memory. The memory  115  can store digital data, which can be displayed on a display device  165 . 
     The input section  135  may also be coupled to the combinatorial logic  170  via line  145  so that the combinatorial logic  170  can receive the input signal  140 . The combinatorial logic  170  may also receive digitized data from the memory  115  via line  125 . The term “combinatorial mask triggering logic” or “combinatorial logic” refers to analog circuits, digital circuits, hardware circuits, firmware, and/or software, or any suitable combination thereof, for processing an input signal and producing a trigger signal based on a predefined set of criteria. 
     The combinatorial mask triggering logic  170  may process the digital data received at input in real-time and generate a trigger signal  150  upon occurrence of a trigger event. The combinatorial mask triggering logic  170  may include mask test circuitry  175 , and may trigger the oscilloscope  105  based on criteria determined at least in part by the mask test circuitry  175 . The mask test circuitry  175  can determine in real-time whether pixels that are associated with the digital data and drawn on the display device  165  bear a predefined relationship to a trigger mask in terms of space and time, as further described below. Moreover, the combinatorial mask triggering logic  170  and mask test circuitry  175  can process the input signal and make such determinations in the frequency domain, time domain, or both. Example embodiments of the functioning and other aspects of the combinatorial mask triggering logic  170  are described below. 
     A processor  155  may be coupled to the combinatorial mask triggering logic  170  and may receive the trigger signal  150 . The processor  155  may also be coupled to the display  165 . The processor  155  may coordinate the processing of data between the input  135 , the combinatorial logic  170 , the memory  115 , and the display  165 , and may cause trigger information, waveform information, and/or other measurement information to be displayed on the display  165 . 
       FIG. 2  illustrates a flow diagram  200  showing a technique for combinatorial mask triggering in terms of space and time in accordance with embodiments of the present invention. The technique may begin at  205  where one or more trigger masks are configured. A “trigger mask” is a mask region defined relative to the drawing plane of the display device  165  (of  FIG. 1 ). The combinatorial mask triggering logic  170  (of  FIG. 1 ) can determine whether a waveform intersects the trigger mask or mask region, or otherwise bears a predefined relationship to the trigger mask or mask region. Although the trigger mask(s) are primarily represented herein as rectangular in shape, it will be understood that the trigger mask(s) may be circular, triangular, linear, or any other suitable shape and size. In the example embodiments described herein, the one or more trigger masks may be configured manually or visually by a user of the oscilloscope, for example, using any suitable input means such as a keyboard, mouse, touch screen, and the like. Alternatively, the one or more trigger masks may be automatically configured by the oscilloscope. The oscilloscope may configure the one or more trigger masks based on previously stored criteria. In addition, the one or more trigger masks can be made using software on an external computer system and then imported into the oscilloscope. 
     The flow proceeds to  210 , where the input signal is received and digitized to produce digital data. A determination is made at  220  whether pixels or components that are associated with the digital data bear a predefined relationship to one or more trigger masks in terms of space and time. If so, then a mask failure occurs, and the combinatorial logic  170  (of  FIG. 1 ) generates a trigger signal at  225 , which triggers the oscilloscope, thereby causing the incoming signal and associated digital data to be stored, at step  230 , in the memory  115  (of  FIG. 1 ). 
     Making the determination of whether the pixels or components bear the predefined relationship can include, for example, determining whether the pixels or components associated with the digital data would violate one or more trigger masks if drawn on the display of the display device. If no mask violation occurs, the digital data is discarded and more is acquired. 
       FIGS. 3A-3B  illustrate a trace  300  and an associated flow diagram  303 , respectively, in accordance with an embodiment of the present invention. The horizontal axis of the spectrum trace  300  (and other spectrum traces described and illustrated herein) can be expressed or measured in terms of frequency when analyzing the input signal in the frequency domain, or in terms of time when analyzing the input signal in the time domain. The vertical axis can be expressed or measured in terms of amplitude or power. This description of the axes also applies to the plots and traces discussed below. 
     At  305  of the flow diagram  303 , a trigger mask  302  can be configured. At  310 , the input signal is received and digitized to produce digital data. 
     A determination is made at  320  whether pixels or components (e.g.,  301 ) associated with the digital data bear a predefined relationship in space to the trigger mask  302 . The predefined relationship can be, for example, an excursion into, through, and/or out of the trigger mask  302 . The excursion can be caused by, for example, the main signal, a glitch in the signal, or some other spurious signal. Another determination is made at  325  whether the predefined relationship is present for a period of time that is the same as, longer than, and/or shorter than a predefined time threshold. In other words, if the pixels or components are detected to cause an excursion and dwell within the associated trigger mask for the period of time that is the same as the predefined time threshold, longer than the predefined threshold, shorter than the predefined threshold, or any combination thereof, then a mask failure occurs and the flow proceeds along the YES path. 
     The determinations made at  320  and  325  can be made as a single combined logical determination based on the space and time factors. If either of the conditions is not met, the flow returns to  310  for further processing. Otherwise, the flow proceeds to  330 , where a trigger signal is produced in response to the satisfied trigger criteria, and then to  335 , where the digital data associated with the incoming signal is stored to the memory. 
     A representation  301  of the digital data can be displayed as a spectrum trace in the frequency domain on a display of the display device  165 , or as a trace in the time domain on the display of the display device  165 . It will be understood that the while the representation  301 , and other representations of digital data illustrated and described herein, often show a single waveform or line, this is to aid in a more simple and direct illustration and explanation, and any number of frequency components, time domain components, waveforms, shapes, lines, traces, and the like, can be present and otherwise drawn on the display device, and processed by the combinatorial mask triggering logic, and still fall within the scope of the inventive techniques described herein. 
       FIGS. 4A-4C  illustrate a first trace  400 , a second trace  408 , and an associated flow diagram  403 , respectively, in accordance with another embodiment of the present invention. When operating within the frequency domain, the spectrum traces  400  and  408  represent frequency components  401  shifting or moving in time. When operating within the time domain, the traces  400  and  408  represent time domain components appearing at different times. The technique may begin at  405 , where a first trigger mask  402  and a second trigger mask  404  are configured. The flow proceeds to  410  where the input signal is received and digitized to produce digital data. 
     Thereafter, either of paths A or B can be taken. Path A indicates an operation being performed within the frequency domain while path B indicates an operation being performed within the time domain. If path A is taken, the flow proceeds to  420  where a determination is made whether one or more frequency components (e.g.,  401 ) in the spectrum trace move between the first trigger mask  402  and the second trigger mask  404 . Conversely, if path B is taken, the flow proceeds to  422  where a determination is made whether there are excursions by the time domain trace into, through, and/or out of the first trigger mask  402  and the second trigger mask  404 . The excursions need not occur simultaneously, but rather, can occur sequentially. As mentioned above, the excursions can be caused by, for example, the main signal, glitches in the signal, or other spurious signals. 
     In either case (path A or path B), the flow returns to  425 , where another determination can be made whether the movement or excursions occur within a period of time  406  that is the same as, shorter than, and/or longer than a predefined time threshold. In other words, if the pixels or components are detected to cause an excursion or failure relative to the first trigger mask, and then within a period of time thereafter, the pixels or components are detected to cause an excursion or failure relative to the second trigger mask, in which the period of time is the same as the predefined time threshold, longer than the predefined threshold, shorter than the predefined threshold, or any combination thereof, then the flow proceeds along the YES path. 
     The determinations made at  420 ,  422  and/or  425  can be made as a single combined logical determination based on the space and time factors. If either of the conditions is not met, the flow returns to  410  for further processing. Otherwise, the flow proceeds to  430 , where a trigger signal is produced in response to the satisfied trigger criteria, and then to  435 , where the digital data associated with the incoming signal is stored to the memory. 
     In an alternative embodiment, the flow skips step  425 . In other words, if path A is taken, the oscilloscope can be triggered if frequency components are present within the first trigger mask  402  and the second trigger mask  404 , without respect to time. If path B is taken in this scenario, the oscilloscope can be triggered if components of the time domain trace are present within the first trigger mask  402  and the second trigger mask  404 , without respect to time. 
     When operating in the frequency domain, a representation  401  of the digital data can be displayed as a spectrum trace on a display of the display device  165 . When operating in the time domain, a representation  401  of the digital data can be displayed as a time domain trace on the display of the display device  165 . 
       FIGS. 5A-5B  illustrate a trace  500  and an associated flow diagram  503 , respectively, in accordance with yet another embodiment of the present invention. The technique may begin at  505  where a plurality of trigger masks  502  are configured. The flow proceeds to  510  where the input signal is received and digitized to produce digital data. 
     Thereafter, either of paths A or B can be taken. Path A indicates an operation being performed within the frequency domain while path B indicates an operation being performed within the time domain. If path A is taken, the flow proceeds to  520  where a determination is made whether frequency components (e.g.,  501 ) in the spectrum trace are present within one or more of the trigger masks  502 . Conversely, if path B is taken, the flow proceeds to  522  where a determination is made whether there are excursions by the time domain trace into, through, and/or out of one or more of the trigger masks  502 . 
     Such determinations can be combined with a determination (not shown) of whether the pixels or components  501  are present within the one or more trigger masks  502  and dwell for a time period that is the same as, longer than, and/or shorter than a predefined time threshold. By way of another example, the determination can be whether the pixels or components  501  are present within 2 of the 4 trigger masks  502 , or 3 of the 4 trigger masks  502 , and so forth. If the condition(s) are not met, the flow returns to  510  for further processing. Otherwise, the flow proceeds to  530 , where a trigger signal is produced in response to the satisfied trigger criteria, and then to  535 , where the digital data associated with the incoming signal is stored to the memory. 
     When operating in the frequency domain, a representation  501  of the digital data can be displayed as a spectrum trace on the display of the display device  165 . For example, the spectrum trace may show a representation  501  of a frequency hopping signal. When operating in the time domain, a representation  501  of the digital data can be displayed as a time domain trace on the display of the display device  165 . 
       FIGS. 6A-6B  illustrate a trace  600  and an associated flow diagram  603 , respectively, in accordance with still another embodiment of the present invention. The technique may begin at  605  where a plurality of trigger masks  602  are configured. The flow proceeds to  610  where the input signal is received and digitized to produce digital data. 
     Thereafter, either of paths A or B can be taken. Path A indicates an operation being performed within the frequency domain while path B indicates an operation being performed within the time domain. If path A is taken, the flow proceeds to  620  where a determination is made whether frequency components (e.g.,  601 ) in the spectrum trace are absent from one or more of the trigger masks  602 . Conversely, if path B is taken, the flow proceeds to  622  where a determination is made whether there is an absence of excursions by the time domain trace from one or more of the trigger masks  502 . 
     Such a determinations can be combined with a determination (not shown) of whether the pixels or components  601  are absent from the one or more trigger masks  602  for a time period that is the same as, longer than, and/or shorter than a predefined time threshold. By way of another example, the determination can be whether the pixels or components  601  are absent from 2 of the 4 trigger masks  602 , or 3 of the 4 trigger masks  602 , and so forth. If the condition(s) are not met, the flow returns to  610  for further processing. Otherwise, the flow proceeds to  630 , where a trigger signal is produced in response to the satisfied trigger criteria, and then to  635 , where the digital data associated with the incoming signal is stored to the memory. 
     A time relationship can also be used as part of the trigger criteria in this embodiment. For example, if there are no pixels or components (e.g.,  601 ) of the signal that are present in any one or more of the trigger masks for a period of time that is the same as, longer than, or shorter than a predefined time threshold, then the trigger criteria can be satisfied, and the trigger signal generated. 
     When operating in the frequency domain, a representation  601  of the digital data can be displayed as a spectrum trace on the display of the display device  165 . For example, the spectrum trace may show a representation  601  of a frequency hopping signal. When operating in the time domain, a representation  601  of the digital data can be displayed as a time domain trace on the display of the display device  165 . 
       FIGS. 7A-7D  illustrate a first trace  700 , a second trace  705 , an associated flow diagram  703  relative to the frequency domain, and an associated flow diagram  803  relative to the time domain, respectively, in accordance with another embodiment of the present invention. 
     Referring to  FIGS. 7A, 7B, and 7C , it is assumed that the traces  700  and  705  are spectrum traces within the frequency domain. The technique may begin at  705 , where a first trigger mask  702  and a second trigger mask  704  are configured. The flow proceeds to  710  where the input signal is received and digitized to produce digital data. 
     A determination is made at  720  whether first frequency components  701  in the spectrum trace are present within the first trigger mask  702 . If NO, the flow returns to  710  for further data acquisition. Otherwise, if YES, then trigger can be armed at  722 , or in other words, the combinatorial mask triggering logic  170  (of  FIG. 1 ) can arm trigger criteria associated with the second trigger mask  704 . Once the trigger is armed, the system continues to acquire and digitize data at  723  looking for a second trigger mask failure. To detect the second trigger mask failure, another determination can be made at  725  whether a density value of second frequency components  707  in the spectrum trace meet or exceed a predefined density threshold associated with the second trigger mask  704 . If YES, then flow proceeds to  730 , where a trigger signal is produced in response to the satisfied trigger criteria, and then to  735 , where the digital data associated with the incoming signal is stored to the memory. Otherwise, if NO, then the flow proceeds to  726 , where yet another determination is made whether the trigger logic has been reset. If the trigger logic has been reset, then the flow returns to  710  for further processing. Otherwise, if the trigger logic has not been reset, then the flow returns  723  for further data acquisition. The reset can come from a user request or from a reset indicator within the digital data. 
     The “density value” can equal the number of “hits” or “excursions” or “pixels” drawn within the associated trigger mask divided by the number of waveforms used to generate it. As used herein, a mask failure can be either a “one time” event (i.e., occurring when a single waveform violates a mask region) or a “statistical” event (i.e., occurring when there have been a certain number of mask failures over a specified time period—typically one frame). Put differently, the term “mask failure” as used herein applies to either a one-time (mask) failure or a statistical (density) failure. 
     In some embodiments, three trigger masks (e.g.,  702 ,  704 , and  708 ) can be used by the combinatorial mask triggering logic. For example, a determination can be made whether an excursion or failure occurs with respect to trigger mask  702 , which can cause trigger criteria to be armed for trigger mask  704 . The oscilloscope can then be triggered in response to an excursion or failure of the trigger mask  704  unless an excursion happens first with respect to the trigger mask  708 . Any suitable combination of trigger masks with respect to space and time, and combinatorial logic, can be used to trigger the oscilloscope. As mentioned above, the excursions can be caused by, for example, the main signal, glitches in the signal, or other spurious signals. 
     In an alternative embodiment, the trigger criteria associated with trigger mask  704  is not related to density, but rather, the presence or excursion of frequency components, similar to the examples above. In other words, the combinatorial mask trigger logic can use trigger masks  702 ,  704 , and/or  708  (in addition to still other trigger masks) to build a sequence of events based on the presence of pixels or components within the trigger masks, with the added option of timing relationships similar to those described above, by which ultimately the trigger criteria is met and the trigger signal generated. 
     When operating in the frequency domain, a representation (e.g.,  701 ) of the digital data can be displayed as a spectrum trace on the display of the display device  165 . 
     Referring now to  FIGS. 7A, 7B, and 7D , it is assumed that the traces  700  and  705  are spectrum traces within the time domain. The technique may begin at  805 , where a first trigger mask  702  and a second trigger mask  704  are configured. The flow proceeds to  810  where the input signal is received and digitized to produce digital data. 
     A determination is made at  820  whether first components  701  in the time domain trace are present within the first trigger mask. If NO, the flow returns to  810  for further data acquisition. Otherwise, if YES, then trigger can be armed at  822 , or in other words, the combinatorial mask triggering logic  170  (of  FIG. 1 ) can arm trigger criteria associated with the second trigger mask  704 . Once the trigger is armed, the system continues to acquire and digitize data at  823  looking for a second trigger mask failure. To detect the second trigger data, another determination can be made at  825  whether second components  707  in the time domain trace are present within the second trigger mask  704 . If YES, then flow proceeds to  830 , where a trigger signal is produced in response to the satisfied trigger criteria, and then to  835 , where the digital data associated with the incoming signal is stored to the memory. Otherwise, if NO, then the flow proceeds to  826 , where yet another determination is made whether the trigger logic has been reset. If the trigger logic has been reset, then the flow returns to  810  for further data acquisition. Otherwise, if the trigger logic has not been reset, then the flow returns  823  for further data acquisition. The reset can come from a user request or from a reset indicator within the digital data. 
     Alternatively, three trigger masks (e.g.,  702 ,  704 , and  708 ) can be used by the combinatorial mask triggering logic in the time domain. For example, a determination can be made whether an excursion occurs with respect to trigger mask  702 , which can cause trigger criteria to be armed for trigger mask  704 . The oscilloscope can then be triggered in response to an excursion of the trigger mask  704  unless an excursion happens first with respect to the trigger mask  708 . Any suitable combination of trigger masks with respect to space and time, and combinatorial logic, can be used to trigger the oscilloscope. 
     In an alternative embodiment, timing relationships between the mask failures are used to determine whether to generate the trigger signal. When a timing relationship is used, for example, the combinatorial mask triggering logic can determine whether the second components (e.g.,  707 ) that are associated with the digital data bear the predefined relationship (e.g., an excursion and/or a dwelling within) to the second trigger mask (e.g.,  704 ) within a predefined period of time after the first components (e.g.,  701 ) that are associated with the digital data are determined to bear the predefined relationship with the first trigger mask (e.g.,  702 ). 
     In an alternative embodiment, the trigger criteria associated with trigger mask  704  is not based solely on the presence or dwelling of components, but rather, it can also be based on the density of components, similar to the examples above. In other words, the combinatorial mask trigger logic can use trigger masks  702 ,  704 , and/or  708  (in addition to still other trigger masks) to build a sequence of events based on the presence and/or density of pixels or components within the trigger masks, with the added option of timing relationships similar to those described above, by which ultimately the trigger criteria is met and the trigger signal generated. 
     When operating in the time domain, a representation (e.g.,  701 ) of the digital data can be displayed as a time domain trace on the display of the display device  165 . 
     The combinatorial and sequential criteria that combines both space and time elements, as discussed herein, can be implemented in either the frequency domain, the time domain, or both. It will be understood that the determinations and other steps in the flow diagrams need not occur in the specific order as described, but rather, these determinations can be made at different times. It will also be understood that the steps described in these techniques need not necessarily occur in the order as illustrated or described. 
     Although the foregoing discussion has focused on particular embodiments, other configurations are contemplated. For example, the combinatorial mask triggering logic  170  (of  FIG. 1 ) can determine whether at least one trigger mask experiences a failure (e.g., excursion into, out of, or through the trigger mask) every N seconds, and if so, trigger the oscilloscope. By way of another example, the combinatorial mask triggering logic  170  can determine whether at least one trigger mask experiences a failure (e.g., excursion into, out of, or through the trigger mask) at least X times per second, and if so, trigger the oscilloscope. 
     As explained above, the combinatorial mask triggering logic  170  can cause the oscilloscope to be triggered when a glitch or other component is present in a waveform for a certain period of time, or when it isn&#39;t present for a specified period of time. 
     In the time domain, the combinatorial mask triggering logic  170  can cause the oscilloscope to be triggered when glitches in a trace occur at a certain rate. The combinatorial mask triggering logic  170  can cause the oscilloscope to be triggered when one glitch (defined by one trigger mask region) occurs within a certain time period after a glitch defined by another trigger mask region. 
     In the frequency domain, the combinatorial mask triggering logic  170  can cause the oscilloscope to be triggered when a spurious component or other frequency component dwells in, or is absent from, a trigger mask region for too long, or too quickly. The combinatorial mask triggering logic  170  can cause the oscilloscope to be triggered when one or more frequency components in a spectrum trace move between one trigger mask region and another too quickly, or too slowly. The combinatorial mask triggering logic  170  can cause the oscilloscope to be triggered when certain spectral components are present in a spectrum trace, but others are absent. The combinatorial mask triggering logic  170  can arm a trigger with a frequency excursion into one trigger mask region, and then trigger when the density is exceeded in another region. The trigger can be limited to cases when the density excursion occurs only within a certain time region after the arming event. 
     Because the combinatorial mask triggering logic  170  may include and utilize the mask test circuitry  175 , such circuitry can catch intermittent events that might never be seen by a purely software implementation. While the embodiments herein need not include a hardware implementation, such an implementation can increase the speed by which the inventive functionality is performed. 
     The various embodiments disclosed herein can recognize “hits” or “excursions” of pixels relative to one or more of the trigger mask regions. The hits or excursions can be combined in multiple regions, together with flexible logic, to create more complex mask failure criteria. Timing relationships between the mask failures can be established and/or chained into a sequence of events. The number of complex mask failures can be counted over a specified time period. These capabilities can be implemented in hardware as the failures occur (i.e., in real-time), or can be implemented in software. A hybrid of hardware and software can be used, such as providing a hardware “flag” when a trigger mask failure occurs, which notifies the software to process the failure. 
     The following discussion is intended to provide a brief, general description of a suitable machine or machines in which certain aspects of the inventive concept can be implemented. Typically, the machine or machines include a system bus to which is attached processors, memory, e.g., random access memory (RAM), read-only memory (ROM), or other state preserving medium, storage devices, a video interface, and input/output interface ports. The machine or machines can be controlled, at least in part, by input from conventional input devices, such as keyboards, mice, etc., as well as by directives received from another machine, interaction with a virtual reality (VR) environment, biometric feedback, or other input signal. As used herein, the term “machine” is intended to broadly encompass a single machine, a virtual machine, or a system of communicatively coupled machines, virtual machines, or devices operating together. Exemplary machines include computing devices such as personal computers, workstations, servers, portable computers, handheld devices, telephones, tablets, etc., as well as transportation devices, such as private or public transportation, e.g., automobiles, trains, cabs, etc. 
     The machine or machines can include embedded controllers, such as programmable or non-programmable logic devices or arrays, Application Specific Integrated Circuits (ASICs), embedded computers, smart cards, and the like. The machine or machines can utilize one or more connections to one or more remote machines, such as through a network interface, modem, or other communicative coupling. Machines can be interconnected by way of a physical and/or logical network, such as an intranet, the Internet, local area networks, wide area networks, etc. One skilled in the art will appreciate that network communication can utilize various wired and/or wireless short range or long range carriers and protocols, including radio frequency (RF), satellite, microwave, Institute of Electrical and Electronics Engineers (IEEE) 545.11, Bluetooth®, optical, infrared, cable, laser, etc. 
     Embodiments of the inventive concept can be described by reference to or in conjunction with associated data including functions, procedures, data structures, application programs, etc. which when accessed by a machine results in the machine performing tasks or defining abstract data types or low-level hardware contexts. Associated data can be stored in, for example, the volatile and/or non-volatile memory, e.g., RAM, ROM, etc., or in other storage devices and their associated storage media, including hard-drives, floppy-disks, optical storage, tapes, flash memory, memory sticks, digital video disks, biological storage, etc. Associated data can be delivered over transmission environments, including the physical and/or logical network, in the form of packets, serial data, parallel data, propagated signals, etc., and can be used in a compressed or encrypted format. Associated data can be used in a distributed environment, and stored locally and/or remotely for machine access. Embodiments of the inventive concept may include a non-transitory machine-readable medium comprising instructions executable by one or more processors, the instructions comprising instructions to perform the elements of the inventive concept as described herein. 
     Other similar or non-similar modifications can be made without deviating from the intended scope of the inventive concept. Accordingly, the inventive concept is not limited except as by the appended claims.