DETAILED DESCRIPTION

[0043] The present invention is a waveform magnification system and method that may be implemented in any signal measurement system having a graphical user interface. In one preferred embodiment of the present invention, the system is implemented in a test and measurement instrument, such as a digital or analog oscilloscope, logic analyzer, network analyzer, spectrum analyzer, or waveform generator. FIG. 1 is a functional block diagram of an exemplary digital oscilloscope suitable for implementing the waveform magnification system and method of the present invention.

[0044] The digital oscilloscope 100 is a commonly-available digital oscilloscope designed to acquire, analyze, and display a wide variety of signals generally in terms of signal voltage versus time. The digital oscilloscope 100 preferably includes a general purpose computer system, which is programmable using a high-level computer programming language and specially programmed, special purpose hardware for performing signal acquisition, analysis and display functions.

[0045] The digital oscilloscope 100 includes a processor 102 , a memory unit 104 , input/output interface cards 106 , storage units 117 such as a hard disk drive and a floppy disk drive, one or more input devices such as front panel keyboard 108 and pointing devices 110 and display 112 . The memory 104 is used for storage of program instructions and for storage of results of calculations performed by the processor 102 . In a preferred embodiment, the memory 104 includes random access memory (RAM). The display 112 is preferably a liquid crystal display and is logically or physically divided into an array of picture elements referred to as pixels. The inputs/output interface cards 106 may be modem cards, network interface cards, sound cards, etc.

[0046] The processor 102 is typically a commercially available processor such as the Pentium microprocessor, PowerPC microprocessor, SPARC processor, PA-RISC processor or a 68000 series microprocessor. Many other processors are also available. Such a processor usually executes a program referred to as an operating system 114 such as the various versions of the Windows operating systems from Microsoft Corporation, the NetWare operating system available from Novell, Inc., or the Unix operating system available from many vendors such as Sun Microsystems, Inc. and Hewlett Packard. The operating system 114 controls the execution of other computer programs such as a graphical user interface (GUI) 116 and the waveform magnification system 118 , and provides scheduling, input/output control, file and data management, memory management and related services. The processor 102 and operating system 114 define a computer platform shown by dashed block 101 , for which application programs and high-level programming languages are written. The functional elements of the digital oscilloscope 100 communicate with each other via one or more buses 120 .

[0047] The digital oscilloscope 100 includes a signal acquisition sub-system 122 , a scope interface sub-system 124 and a video display control sub-system 126 . The signal acquisition sub-system 122 includes a scaling and conditioning unit 128 that receives input signals through channel inputs 130 . The scaling and conditioning unit 128 and acquisition unit 132 include well-known high frequency electronics for signal acquisition, signal conditioning and analog-to-digital conversion, all of which are controlled by the computer system 101 and are considered to be well-known in the art. The time base unit 134 drives the analog-to-digital process performed by the acquisition unit 132 , specifying when to sample the input signals and the number of samples to be taken. The trigger circuitry 136 synchronizes the acquisition process through the time base 134 , enabling the operator to arrange a trigger event to obtain a stable waveform display of the desired features of one or more of the input signals. Trigger circuitry 136 may be based upon a line sync or auxiliary trigger input as is well-known in the art.

[0048] The waveform analyzer 138 performs measurement processes for developing the waveform for display. The waveform analyzer 138 contains hardware and software components to perform well-known operations such as setting the analog-to-digital codes for the acquisition unit 132 and mapping the resulting digital information to the physical pixel locations which are ultimately presented on the display 112 under the control of the graphical user interface 116 . The pointing device 110 and/or the keyboard 108 are used to move a cursor on the GUI-controlled display 112 to select display elements adjacent to or under the cursor. The pointing devices 110 may include any well-known pointing devices is such as a mouse, trackball or joystick. The cursor may additionally be controlled with any one or more keyboards located externally or integrated into a front panel of the digital oscilloscope 100 .

[0049] The scope interface sub-system 124 includes a video controller 140 that controls the rendering of pixels into a waveform random access memory (RAM) 142 . The video control sub-system 126 also receives display element control commands and cursor input information from the front panel keyboard 108 and the pointing device 110 . The waveform RAM 142 includes a data structure for each pixel location on the display 112 . The data structures contain information regarding every display element that is to be drawn at each pixel location. Although there may be multiple display elements which are to be drawn at a given pixel location, only one color may be rendered at that location at any given time. The waveform RAM 142 supplies a priority encoder 144 with information regarding which display elements are to be displayed at each pixel location. The priority encoder 144 prioritizes the competing display elements. For example, if the operator arranged a marker and a waveform such that they are located in the same pixel location, then the priority encoder 144 selects that display element which has the highest predetermined priority. In such an example, the color of the marker is preferably rendered at that pixel location providing a display that appears to show the marker over the competing waveform. The priority encoder 144 then sends the selected color to the video RAM (VRAM) 146 which then causes the pixel to be rendered in the indicated color.

[0050] The video display control subsystem 126 includes a dynamic random access memory (DRAM) 148 which contains data specifying a color for each pixel in the display 112 . Likewise, the VRAM 146 also contains data specifying a color for each pixel in the display 112 . The computer system 101 controls the information and DRAM 148 while the signal acquisition system 122 controls the information in the VRAM 146 . For each pixel in the display 112 , the video display control subsystem 126 selects whether the pixel in the display 112 is to be specified from the VRAM 146 or the DRAM 148 . In general, information in the VRAM 146 includes digitized waveforms being generated by the signal acquisition sub-system 122 with high rates of change which are much too fast for software processing by the computer system 101 for real-time display of the waveforms on the display 112 .

[0051] The video display control sub-system 126 includes a display controller 150 and a multiplexer 152 . The controller 150 controls which of the two inputs to the multiplexer 152 are processed into display signals for transmission to the display 112 under the control of the graphical user interface 116 . The display controller 150 typically monitors color data send from the DRAM 148 and may be programmed to switch to multiplexer 152 to a different input once a particularly programmed color is received from the DRAM 148 . A rectangular pixel area is typically defined within DRAM 148 with the programmed color. The programmed color is not displayed but instead serves as a data path switch control for the multiplexer 152 . Therefore, within the programmed color rectangle, display data comes from VRAM 146 . If various control functions are needed, an interactive dialog box may be drawn within the programmed color rectangle. This, as noted, prevents the information from the VRAM 146 from being displayed in the area occupied by the dialog box.

[0052] The waveform magnification system 118 implements a simple and intuitive method for performing automatic magnification of a desired portion or region of a waveform display presented on the graphical user interface 116 . The waveform magnification system 118 simultaneously displays an original or main waveform display containing the displayed waveforms on a portion of the display and a magnified waveform display displayed on another portion of the display screen. The magnified waveform display provides a magnified view of an operator-selected region of the main waveform display. This region is defined by an extent (scale) and the position (offset) for each of two axes of a selection window positioned over the main waveform display to encompass the desired region to be magnified. The selection window may be positioned by the operator so as to encompass any desired region of the main waveform display and not degrade the informational content present on the main waveform display. In particular, the present invention provides graphical manipulation techniques for controlling the selection window. The selected waveform region displayed in the selection window is graphically associated with the magnified waveform display to assist the operator in visually correlating the informational content of the original and magnified views of the selected waveform region. Through the implementation of various graphical techniques, the present invention clearly displays this association while retaining all of the information of the main waveform display. For example, in one embodiment the selection window is rendered on top of the waveform display to ensure it is not obscured by waveforms and related information displayed on the waveform display. Furthermore, the background color of the main waveform display is altered outside of the region constituting the magnified view so that the contrast between the background and the waveforms is reduced. This communicates a relative importance of the selected and non-selected regions of the main waveform display and associates the selected region with the magnified view. Thus, an operator can observe all information provided by the signal measurement system related to the displayed waveform while concurrently observing a magnified waveform display that is visually associated with a selected waveform display region.

[0053] The software routines for performing the waveform magnification methodology in accordance with the present invention typically resides in memory 104 and/or storage units 117 , and may be stored on a computer-readable medium such as, for example, magnetic disk, compact disk, or magnetic tape, and may be loaded into the digital oscilloscope 100 using an appropriate peripheral device as is known in the art.

[0054] Preferably, the waveform magnification system 118 is implemented in any well-known programming language such as C or C++. Those skilled in the relevant art will appreciate that different implementations, including different function names, programming languages, data structures, and/or algorithms may also be used in embodiments of the present invention other than those described below. It should be further understood that the invention is not limited to a particular computer platform, particular operating system, particular processor, or particular high-level programming language, and that the hardware components identified above are given by way of example only. Portions of the waveform magnification system may be implemented, for example, in dedicated hardware, frameware, or any combination thereof.

[0055] A functional block diagram of one preferred embodiment of the measurement invocation system 118 of the present invention implemented in the digital oscilloscope 100 is shown in FIG. 2 . A preferred implementation of the present invention is in test and measurement equipment having a graphical user interface 116 , such as the digital oscilloscope 100 illustrated in FIG. 1 . The functions and operations of the waveform magnification system 118 will be described below with reference to the exemplary graphical user interface displays illustrated in FIGS. 3A through 3E .

[0056] Referring to FIG. 3 A, when the waveform magnification system 118 of the present invention has not been invoked, a main view window 301 is displayed by the graphical user interface 116 over a substantial portion of the GUI display 300 . The main view window 301 includes a main waveform display 302 on which one or more waveforms and other display elements are presented over a graticule 303 . The waveform display 302 is surrounded by a number of information and control menu bars adjacent to its periphery. One such bar is a measurement toolbar 304 shown to be adjacent to the left-hand side of the waveform display 302 . Other toolbars include a channel status toolbar 311 and a waveform display toolbar 305 . As used herein, the term “view window” refers to a waveform display and associated toolbars that specifically support the information presented on the associated waveform display such as the waveform display toolbar 305 . In the illustrative example shown in FIGS. 3A through 3E , a single waveform 314 is displayed in the main waveform display 302 . The waveform 314 is identified as being a channel 1 waveform on the channel status toolbar 311 shown above the waveform display 302 . On the channel status toolbar 311 , a graphical vertical scale control 313 and a graphical display 312 of a current vertical scale setting are also presented for each channel that has a waveform displayed in the main waveform display 302 . As shown in FIG. 3 A, the vertical scale window 312 indicates that the displayed waveform 314 has a vertical scale of 100 millivolts/division (mv/div).

[0057] The waveform display toolbar 305 provides information pertaining to the horizontal scale and offset of the associated waveform display 302 . The waveform display toolbar 305 includes a horizontal scale control 306 for controlling the horizontal scale of the waveform display, and a horizontal offset control 308 for controlling the horizonal offset of the waveform display 302 . An associated horizontal scale display window 316 presents the current horizontal scale of the waveform display 302 to the operator. Likewise, an associated horizontal offset display window 307 presents the current horizontal offset of the waveform display 302 to the operator. The horizontal scale of the channel one waveform 314 illustrated in FIG. 3A is 100 ns/div with a horizontal offset of 0.0 seconds.

[0058] FIG. 3B is an illustration of the graphical user interface display 300 presented in accordance with one embodiment of the present invention. Upon invocation of the waveform magnification system 118 , a dual window arrangement such as that shown in FIG. 3B is displayed on the GUI display 300 by the present invention in conjunction with the graphical user interface 116 to simultaneously display a main waveform display and a magnified waveform display.

[0059] The display 300 is partitioned among a main view window 320 and a magnified view window 330 . The main view window 320 includes a graticule 322 that is reduced in size from that displayed in FIG. 3A so as to provide sufficient display area for the display of the magnified view window 330 .

[0060] In the illustrative embodiment, the main view window 320 is presented towards the top of the display 300 while the magnified view window 330 is presented towards the bottom of the display 300 . This approach is consistent with traditional oscilloscopes which present a main and magnified view region across the top and bottom of the display 300 , respectively. It should be understood, however that the main view window 320 and the magnified view window 330 may be presented at arbitrary locations and sizings on the display 300 .

[0061] In one embodiment, the portion of the display area that is allocated to each of the view windows 320 and 330 is determined by the current graphical mode of the display 300 . For example, in the illustrative embodiment, the illustrated graphical mode is one in which the measurement toolbar 304 is displayed. In this case, the display area occupied by the toolbar 304 is not available to the view windows 320 and 330 . Accordingly, the processes performed by certain embodiments of the present invention consider the graphical mode of the display 300 when rendering the main view window 320 and the magnified view window 330 . However, in the following discussion, this functionality resides within a graphical user interface 116 which provides the available graticule size and location to the present invention.

[0062] The main view window 320 includes the main graticule 322 and associated supporting window 327 . Likewise, the magnified view window 330 includes the magnified graticule 332 and supporting window 337 . In both instances, the windows 327 , 337 include the associated waveform display toolbar 350 , 360 . The scaling and offset of the main waveform display 326 and the magnified waveform display 336 are controllable through the graphical user interface 116 when in the “dual view mode” of operation. To accomplish this, the waveform display toolbar 360 is assigned to the magnified waveform display 326 while the waveform display toolbar 350 is assigned to the main waveform display 336 . The main waveform display toolbar 350 performs the same functions as the waveform display toolbar 350 illustrated in FIG. 3A . The main waveform display toolbar 350 includes horizontal scale control buttons 352 and window 351 for controlling and displaying the horizontal scale of the main waveform display 326 . The toolbar 350 also includes horizontal offset control buttons 354 and window 353 for controlling and displaying the horizontal offset of the main waveform display 326 . Likewise, the magnified waveform display toolbar 360 has a similar structure and performs similar operations as the main waveform display toolbar 350 . The toolbar 360 includes horizontal scale controls 362 and a horizontal scale window 361 for controlling and displaying the horizontal scale of the magnified waveform display 336 . The toolbar 360 also includes horizontal offset controls 364 and a horizontal offset window 363 for controlling and displaying the horizontal offset of the magnified waveform display 336 . The function and operation of the horizontal offset and scale controls of the magnified waveform display 336 and the corresponding effect on the selection window 340 of the present invention is described in detail below.

[0063] There are analogous horizontal and vertical scale and offset controls on the front panel 108 . The values of such controls are provided to the waveform analyzer 138 . During normal operations, these scale and offset controls provide an operator with the ability to adjust the associated parameter of the main waveform display 302 illustrated in FIG. 3A . In one embodiment of the present invention, the front panel offset and scale controls are reassigned to control the horizontal scale and offset of the magnified waveform display 336 when the magnified view window 330 is displayed. This is shown in FIG. 2 by the front panel 108 providing to the waveform analyzer 138 the magnified view scale and offset control data 254 . In an alternative embodiment, the original assignments are maintained and the front panel 108 implements soft keys to generate the magnified view scale and offset control inputs 254 . It should be understood that any other method for providing the operator with the ability to control the scale and offset of either waveform display through the front panel 108 may be used. Alternatively, the front panel offset and scale controls may simply be disabled and replaced by graphical controls, such as those shown on the waveform display toolbars 350 and 360 .

[0064] In accordance with one embodiment of the present invention, an operator-controlled magnification selection window 340 is displayed over the main waveform display 326 in the main view window 320 . The selection window 340 encompasses and defines an operator-selected region of the main waveform display 326 for which a magnified waveform display 336 is presented simultaneously in the magnified view window 330 . The selection window 340 is initially displayed on the main waveform display 326 upon invocation of the system 118 . Initially, the selection window 340 is set to a default scale and offset which may be subsequently altered by the operator in accordance with the present invention. In the illustrative embodiment illustrated in FIG. 3 B, the selection window 340 captures the entire vertical extent and the center 10% of the horizontal extent of the main waveform display 326 . Thus, in the embodiment illustrated in FIG. 3 B, the selection window 340 extends horizontally for 0.5 divisions on each side of the horizontal offset to encompass one division of the main waveform display 326 . Since there are 10 horizontal divisions in the illustrated main graticule 322 , the selection window 340 encompasses one division or 10% of the main waveform display 326 .

[0065] In addition to the selection window 340 , display features providing a graphical association between the waveform region 328 and the selection window 340 and the expanded view of the same waveform region in the magnified view window 330 are provided in alternative embodiments of the present invention. In one such embodiment, the background 342 of the selected region 328 of the main waveform display 326 which lies within the selection window 340 is rendered in the same color or gray scale as the background 334 of the magnified waveform display 336 . Furthermore, the background 324 of the main waveform display 326 that is not within the selection window 340 is rendered in a different color or gray scale than the backgrounds 342 , 334 . In the exemplary embodiment illustrated in FIG. 3 B, the contrast between the background 324 and the waveforms 314 displayed in the main waveform display 326 is reduced. For example, when the main waveform background is black, the background 324 is rendered in a gray shade. This communicates to the operator that the information in the non-selected region of the main waveform display 326 is de-emphasized relative to the information within the selection window 340 . Moreover, in a preferred embodiment the background 342 of the selected region 328 and the background 334 of the magnified waveform display 336 are rendered in the same normal background color. This reinforces the association between the two views as well as visually emphasizes the selected region 328 . As shown in FIG. 3 B, this provides an overall graphical display of a magnified view of a windowed region 328 of the main waveform display 326 . This provides an easy and intuitive technique for enabling an operator to associate the selected waveform region 328 and the waveform region displayed in the magnified view window 330 .

[0066] Referring now to FIG. 2 , the waveform magnification system 118 of the present invention broadly includes a magnification selection window determinator 202 and a rendering controller 204 . The determinator 202 determines a horizontal and vertical scale and offset for the operator-controlled selection window 340 and the associated magnified waveform display 336 . The determinator 202 also provides the operator with the ability to graphically manipulate the selection window 340 to achieve a scale and offset so as to encompass a desired region 328 of the main waveform display 326 . As a result, the present invention enables an operator to directly interact with the waveform display to select a desired waveform display region for magnified viewing. Furthermore, the graphical techniques of the present invention enable an operator to select the scale (extent) and offset (position) of the magnified view quickly and easily. Thus, a graphical approach for directly interacting with the waveform display to select for magnification a desired waveform display region is provided.

[0067] The rendering controller 204 controls the rendering of the main view window 320 , magnification view window 330 , and selection window 340 based upon the operator-selected scale and offset values and the graphical mode of the display 300 . The rendering controller 204 also controls the rendering of graphical items that are used to associate the magnified waveform display 336 and the selected region 328 of the main waveform display 326 . This enables the present invention to implement any predetermined graphical technique to clearly communicate the relationship between the contents of the main and magnified view windows while retaining all of the information contained in the main waveform display 326 . Thus, an operator may observe all information provided by the signal measurement system 100 related to the displayed waveforms while simultaneously observing a magnified view of a selected portion of the displayed waveforms.

[0068] FIG. 3C is a diagram illustrating the graphical user interface display 300 of FIG. 3B after an operator has adjusted the position or offset of the selection window 340 . There are a number of available methods to change the scale and offset of the selection window 340 in the illustrated embodiment of the present invention. These include the use of the front panel scale and offset controls, generating the magnification waveform display scale/offset data 254 ; the use of the horizontal offset control buttons 364 on the magnified waveform display toolbar 360 , generating magnified waveform display scale/offset data 262 ; and through the graphical manipulation of the selection window 340 as described below, generating magnified waveform display scale/offset data 258 , all of which are received by the waveform analyzer 138 . Other methods for adjusting the horizontal offset or scale, such as dialog boxes, pull-down menus, etc., are considered to be within the scope of the present invention.

[0069] Regardless of the method employed, the resulting position of the selection window 340 is displayed in the horizontal offset display window 363 in the tool bar 360 . In FIG. 3 C, the selection window 340 is positioned from a horizontal offset of 0.0 seconds ( FIG. 3B ) to a horizontal offset of −200.00 ns. This causes the selection window 340 to travel to a different position on the main waveform display 326 . Note that the offset of the main waveform display 326 has not been adjusted and remains at 0.0 seconds as shown in the horizontal offset window 353 of the main waveform display toolbar 350 .

[0070] FIG. 3D is a diagram illustrating the graphical user interface display 300 illustrated in FIG. 3B after an operator has adjusted the horizontal scale of the selection window 340 and magnified waveform display 332 . Similar methods are available to modify the horizontal scale as those described above for the changing the horizontal offset. The resulting scale of the magnified waveform display 336 and selection window 340 is displayed in the horizontal scale display window 361 of the toolbar 360 . In FIG. 3 D, the horizontal offset of the selection window 340 and magnified waveform display 336 is adjusted from a horizontal scale of 10.0 ns/div. ( FIG. 3B ) to a horizontal scale of 50.00 ns/div. This causes the selection window 340 to encompass a total of five divisions centered about the main horizontal offset value of 0.0 ns (±250 ns). The horizontal scale of all of the displayed waveforms is adjusted accordingly in the magnified waveform display 336 .

[0071] FIG. 3E is a diagram of the graphical user interface display 300 showing the position of the selection window 340 illustrated in FIG. 3B after the horizontal offset of the main waveform display 326 is adjusted. The main waveform display horizontal offset, as shown in the horizontal offset window 353 of the main waveform display toolbar 350 , is adjusted from a value of 0.0 ns ( FIG. 3D ) to a value of 200.000 ns ( FIG. 3E ). Since the magnified waveform display offset remained at 0.0 ns as shown in the horizontal offset window 363 of the toolbar 360 , the selection window 340 is shifted two divisions to the left to remain centered about the magnified horizontal offset of 0.0 ns. It should be understood and observed that the magnified waveform display 336 has not been altered and therefore is the same as that shown in FIG. 3D .

[0072] FIG. 4 is perspective view of the main graticule 322 and magnified graticule 332 created in accordance with one embodiment of the present invention. The location of the graticules 322 and 332 on the graphical user interface display 300 is determined from the graticule locations 264 received from the graphical user interface 116 . The main view window horizontal scale (MainVWHorizScale) 404 represents sweep speed and is in units of time per division. At the center of the horizontal axis is the horizontal offset 406 representing the delay or horizontal position of the displayed waveforms. Together with the main view window vertical scale 451 (in units of volts per division) and a main view vertical offset 460 (in units of volts), these quantities define the main view graticule 322 . The boundaries of a selection window 340 are shown in the main graticule 322 . The boundaries of the selection window 340 are defined by a start and stop pixel column 414 , 416 along the horizontal axis and a start and stop pixel row along the vertical axis.

[0073] The waveform analyzer 138 and the magnification selection window determinator 202 perform various scaling and position calculations to determine the location in which the main waveform display 326 and the magnified waveform display 336 are to be rendered on the graphical user interface display 300 . Furthermore, such calculations are also used to determine the location at which to render the supporting windows 327 , 337 . For ease of description, these calculations will be described with reference to one particular embodiment of the present invention wherein the vertical extent of the selection window 340 is not adjustable by the operator and is fixed to include the entire vertical extent of the main waveform display 326 . In such an embodiment, the start and stops rows 417 and 418 coincide with the main view window top limit 401 and bottom limit 403 , respectively. The main view window graph left limit (MainVWLeftLimit) 408 and the main view window graph right limit (MainVWRightLimit) 410 are the pixel location limits on the display 300 for the main view graticule 322 . These values are provided to the waveform magnification system 118 by the graphical user interface 116 in the graticule locations data 264 .

[0074] The main view window horizontal displayed range (MainVWHDispRng) 402 is the time across the entire main graticule 322 . The main view window horizontal display range 402 is the product of the number of horizontal divisions in the main graticule 322 (MainGratDiv) and the current horizontal scale (MainVWHorizScale) 404 . The current horizontal scale may be a default or operator selected value and is displayed in the horizontal scale window 351 of the main waveform display toolbar 350 . As will be described in detail below, the number of horizontal divisions in the main graticule 322 and the current horizontal scale values are provided as inputs to the magnification system 118 from the waveform analyzer 138 as part of the main/mag display parameters 250 . In the illustrative embodiment shown in FIGS. 3B and 4 , this would result in: 1 $\begin{array}{c}\mathrm{MainVWHorizDispRng}=\left(\mathrm{MainGratDiv}\right)\left(\mathrm{MainVWHorizScale}\right)\\ =\left(10\mathrm{div}\right)\left(100\mathrm{ns}\text{/}\mathrm{div}\right)\\ =1000\mathrm{ns}\end{array}$

[0075] As is well known, this display range is centered about the horizontal offset 406 .

[0076] The main view window graph left limit (MainVWLeftLimit) 408 and main view window graph right limit (MainVWRightLimit) 410 are the pixel location limits of the main view graticule 322 . The main view window horizontal display origin (MainVWHDispOrig) 412 is the time at the left edge of the main view graticule 322 (that is, at the MainVWLeftLimit 408 ). This is determined based upon the horizontal offset 406 and the main view window horizontal displayed range 402 . In the illustrative embodiment illustrated in FIGS. 3B and 4 , this would yield: 2 $\begin{array}{c}\mathrm{MainVWHorizDispOrig}=\left(\mathrm{HorizOffset}\right)-\left(\mathrm{MainVWHorizDispRange}\right)/2\\ =\left(0.0\sec \right)-\left(1000\mathrm{ns}\right)/2\\ =-500\mathrm{ns}\end{array}$

[0077] As noted, the horizontal offset 406 and the horizontal scale 404 are provided to the waveform analyzer 138 from the graphical user interface 116 via the main view window scale/offset input 260 . In accordance with one embodiment of the present invention, the horizontal offset 406 and scale 404 of the main view window are graphically controllable and provided to the waveform analyzer 138 by the determinator 202 via a main view window scale/offset input 254 . In addition, the number of horizontal divisions in the main graticule 322 is provided to the waveform analyzer 138 as part of graphical locations 264 generated by the graphical user interface 116 . The above values for the main view window horizontal display range 402 and the main view window horizontal display origin 412 are provided to the magnification selection window determinator 202 as part of the main/mag display parameters 250 from the waveform analyzer 138 .

[0078] Similar scaling calculations are also performed for the magnified view. A magnified view window displayed range (MagVWHDispRng) 420 is the product of the number of horizontal divisions in the magnified graticule 332 (MagGratDiv) and the current magnified horizontal scale (MagVWHorizScale) 424 . The current magnified horizontal scale 424 may be set, as noted, by any of the above methods and displayed in the horizontal scale window 361 of the waveform display toolbar 360 . In the illustrative embodiment shown in FIGS. 3B and 4 , this would result in: 3 $\begin{array}{c}\mathrm{MagVWHorizDispRng}=\left(\mathrm{MagGratDiv}\right)\left(\mathrm{MagVWHorizScale}\right)`\\ =\left(10\mathrm{div}\right)\left(10\mathrm{ns}\text{/}\mathrm{div}\right)\\ =100\mathrm{ns}\end{array}$

[0079] As is well known, this range is centered about the horizontal offset 426 .

[0080] The magnified view window horizontal display origin (MagVWHDispOrig) 422 is the time at the left edge of the magnified view graticule 332 (at MagVWLeftLimit 428 ). This is determined based upon the horizontal offset 426 and the magnified view window horizontal displayed range 420 . In the illustrative embodiment illustrated in FIGS. 3B and 4 , this would yield: 4 $\begin{array}{c}\mathrm{MagVWHorizDispOrig}=\left(\mathrm{HorizOffset}\right)-\left(\mathrm{MagVWHorizDispRange}\right)/2\\ =\left(0.0\sec \right)-\left(100\mathrm{ns}\right)/2\\ =-50\mathrm{ns}\end{array}$

[0081] The above values may also be calculated based upon the ratio between the current graticule size and scale settings of the main and magnified views. A window ratio representing the ratio of waveform displays on the main and magnified view windows is calculated as the ratio of the main view window displayed range (MainVWDispRange) and the magnified view window displayed range (MagVWDispRange). In the illustrative embodiment illustrated in FIGS. 3B and 4 , this would yield: 5 $\begin{array}{c}\mathrm{WindowRatio}=\left(\mathrm{MagVWDispRng}\right)/\left(\mathrm{MainVWDispRng}\right)\\ =\left(100\mathrm{ns}\right)/\left(1000\mathrm{ns}\right)\\ =10\%\end{array}$

[0082] And, therefore,

MagVWHorizDispRng =( MainVWHorizDispRng )( WindowRatio )

[0083] In the illustrative embodiment, the magnification selection window determinator 202 receives the above values from the waveform analyzer 138 and determines the pixel locations identifying the selection window boundaries. In the illustrative embodiment wherein the horizontal extent is controllable by the operator, a magnification selection window start column (MagSelWinStartCol) 414 and a magnification selection window stop column (MagSelWinStopCol) 416 are determined. The start and stop columns 414 , 416 are pixel location values for subsequent rendering by the rendering controller 204 . The above values provided by the waveform analyzer 138 are time-based values. Accordingly, the selection window start and stop column calculations must convert time-based parameters to pixel values.

[0084] The magnification selection window start column 414 is determined by first dividing the difference of the beginning time of the selection window and the beginning time of the main view window by the total time represented by the main view window. The result of this calculation (a fraction between 0 and 1) is then multiplied by the total horizontal pixel range of the main view window. This gives a number of pixels which, when added to the pixel value representing the left hand edge of the main view window, yields the start column. In the illustrative embodiment illustrated in FIGS. 3B and 4 , this would yield: 6 $\begin{array}{c}\mathrm{MagSelWinStartCol}=[(\left(\mathrm{MagVWHorizDispOrig}\right)-\\ \left(\mathrm{MainVWHorizDispOrig}\right))/\\ \left(\mathrm{MainVWHorizDispRng}\right)]*\\ \left[\left(\mathrm{MainVWRightLimit}\right)-\left(\mathrm{MainVWLeftLimit}\right)\right]+\\ \mathrm{MainVWLeftLimit}\\ =\left[\left(\left(-50\mathrm{ns}\right)-\left(500\mathrm{ns}\right)\right)/1000\mathrm{ns}\right)]*\\ [\left(\left(\mathrm{Pixel}609\right)-\left(\mathrm{Pixel}59\right)\right]+\mathrm{Pixel}59\\ =\mathrm{Pixel}307\end{array}$

[0085] The magnification selection window stop column 416 is determined in a similar manner. In the illustrative embodiment illustrated in FIGS. 3B and 4 , this would yield: 7 $\begin{array}{c}\mathrm{MagSelWinStopCol}=[(\left(\mathrm{MagVWHorizDispOrig}\right)+\\ \left(\mathrm{MagVWHorizDispOrg}\right)-\\ \left(\mathrm{MainVWHorizDispOrig}\right))/\\ \left(\mathrm{MainVWHorizDispRng}\right)]*\\ \left[\left(\mathrm{MainVWRightLimit}\right)-\left(\mathrm{MainVWLeftLimit}\right)\right]+\\ \mathrm{MainVWLeftLimit}\\ =\left[\left(\left(-50\mathrm{ns}\right)+\left(100\mathrm{ns}\right)-\left(-500\mathrm{ns}\right)\right)/\left(1000\mathrm{ns}\right)\right]*\\ [\left(\left(\mathrm{Pixel}609\right)-\left(\mathrm{Pixel}59\right)\right]+\mathrm{Pixel}59\\ =\mathrm{Pixel}362\end{array}$

[0086] The start and stop columns for the selection window are then provided to the rendering controller 204 a part of the selection window boundaries 252 . As noted, the selection window start and stop rows may 417 , 418 may also be calculated in a like manner and provided to the rendering controller 204 as part of the selection window boundaries 252 .

[0087] It should be understood that in alternative embodiments, the calculations performed by the waveform analyzer 138 may be performed by the magnification selection window determinator 202 . However, in the implementing digital oscilloscope 100 , the waveform analyzer 138 currently performs such calculations. Accordingly, the results of those calculations are provided to the determinator 202 in the main/mag display parameters 250 as described above.

[0088] As noted, the selection window determinator 202 determines the selection window boundaries based upon the parameters 250 as described above. In the illustrative embodiment, the determinator 202 receives main and magnified display parameters 250 from the waveform analyzer 138 and uses these parameters to determine the selection window boundaries 252 defining the borders of the selection window 340 in terms of their pixel locations on the display 300 for subsequent rendering by the rendering controller 204 . The determinator 202 also provides the operator with the ability to graphically manipulate the selection window 340 to encompass any desired region of the main waveform display 326 . The determinator receives cursor information 260 from the operating system 114 and determines whether the selection window 340 has been selected by the operator using any available known pointing device. If the operator has graphically modified either the offset or scale of the selection window 340 , the determinator 202 determines the magnified view window scale and offset values and provides them to the waveform analyzer 138 as shown by line 258 . A functional block diagram of one embodiment of the selection window determinator 202 is illustrated in FIG. 5 .

[0089] The selection determinator 202 broadly includes a selection window boundary determinator 502 and a graphical selector 504 . The selection window boundary determinator 502 receives the main/mag display parameters 250 from the waveform analyzer 238 to generate the selection window boundaries 252 as described above. As noted, the display parameters 250 provided by the waveform analyzer 138 include time and graticule data for the main and magnified view windows.

[0090] The graphical selector 504 includes an interface with the digital oscilloscope 100 to obtain cursor information 260 . As noted, the digital oscilloscope 100 is preferably a computer-based system containing computer system 101 . Typically, in such embodiments, display control and status information such as cursor information 260 is obtained from the operating system 114 running on the processor 102 through the generation of well-known procedure calls.

[0091] The cursor information 260 includes a current position 501 of the cursor on the display 300 and a selection indication 503 indicating whether the operator has selected a pixel location on the display 300 . The operator may select a pixel location through well-known pointing devices introduced above, such as a mouse, trackball, track-pad, joystick, keyboard, etc. The cursor information 260 also preferably includes cursor timing 505 which indicates the length of time during the which the cursor remains stationary, or dwells, at a single pixel location. A hit-tester 506 included in the graphical selector 504 determines whether a meaningful pixel location (such as within display 300 ) has been selected by the operator based upon these inputs in a well-known manner. Preferably, the hit tester 506 is the hit tester described in commonly-owned U.S. patent application entitled “System and Method for Efficient Hit-Testing in a Graphical User Interface,” naming as an inventor Jay A. Alexander and filed under Attorney Docket No. 10961062 on May 27, 1997, the specification of which is hereby incorporated by reference in its entirety.

[0092] The hit-test system determines 506 whether the operator has selected a cursor position sufficiently close to a display element to be considered a selection by the operator of that display element. As noted, a display element may include a waveform, vertical or horizontal markers, etc. The hit-tester 506 generates a display element selected output 511 to indicate such a selection. The hit-tester 506 also generates a graphical selection 509 indicating whether it has received a selection indication 503 from the operating system 104 . Furthermore, the hit-tester 506 generates a current cursor position 507 based upon the cursor position 501 received from the operating system 114 . It should be understood that the graphical selector 504 may include or interface with any other means for determining whether a meaningful pixel location has been selected by the operator based upon the above or other inputs and using other techniques now or later developed. The graphical selector 504 also includes a selection window manipulation controller 508 for determining whether the operator selected the selection window 340 . In one embodiment of the present invention, the controller 508 performs the following operations when the hit-tester 506 determines that a graphical selection has been made but that a display element has not been selected. Thus, such a selection indicates either that the operator has selected the background region or, possibly the selection window 340 . The selection window 340 is determined to be selected if the cursor is at or adjacent to the selection window boundary. To determine whether the selection window 340 has been selected, the controller 508 divides the pixels in the display 300 into three regions. FIG. 9 is a perspective view of the selection window 340 and the pixel regions created by the controller 508 in accordance with one embodiment of the present invention. The three regions are defined by an outer boundary