GB2214764A - Pixel intensity modulation in a waveform display - Google Patents

Abstract

A digital oscilloscope produces a waveform display in response to waveform data sequences acquired by sucessively digitizing an input signal. The waveform display represents the magnitude of the input signal as a function of time by selectively illuminating pixels of an array of pixels on the screen, wherein each pixel represents a different combination of input signal magnitude and time. The intensity of each pixel of the array is an increasing function of the number of acquired waveform data sequence elements having associated therewith a magnitude and relative sampling time most nearly similar to a magnitude and relative sampling time represented by the pixel. The intensity of each pixel is also a decreasing function of time. Repetative waveforms therefore show an increase in brightness whereas noise (occupying different time/magnitude coordinates from field to field) rapidly fades. <IMAGE>

Description

PIXEL INTENSITY MODULATION IN A WAVEFORM DISPLAY Background of the Invention The present invention relate. in general to digital oscilloscopes and in particular to an oscilloscope that modulates pixel intensity in a waveform display to provide additional information about input signals In an analog oscilloscope, an electron beam repetitively sweeps horizontally across a screen creating a "trace" of glowing phosphors on the screen. When the magnitude of an input signal controls the vertical position of the beam during its horizontal sweep across the screen, the trace provides a waveform display representing the behavior of the input signal as a function of time.

A waveform produced by a single beam sweep eventually fades out, but when the input signal is periodic and beam sweeps are periodically initiated at similar points during similar cycles of the input signal, the beam traces out the same path during each sweep and a stable waveform is continually displayed. When the screen phosphors are persistent enough to glow substantially longer than a single sweep cycle, the waveform display represents a time-weighted record of traces produced by several previous sweeps of the beam and conveys information regarding the behavior of the input signal during more than just the lost recent sweep cycle.

An operator may adjust beam intensity so that screen phosphors become incrementally brighter each time the beam strikes them, and become incrementally dimmer each time the beam misses them during each sweep. Such adjustment helps reduce effects of transient noise on the waveform display inasmuch as temporary vertical excursions of the beam from the waveform trace due to transient noise produce only dim traces that quickly fade away.

But the waveform display remains bright and constant as long as the input signal that it represents remains unchanged.

Digital oscilloscopes aay display waveforms representing magnitudes of input signals as functions of time, the waveforms being formed by selectively illuminating pixels on a cathode ray tube (CRT) screen. Typically, an input signal is sampled and digitized to provide a waveform data sequence, each successive element of the sequence representing the magnitude of the waveform at a successive time. In a raster scan oscilloscope, displays are formed on a screen by selectively illuminating pixels organized into an array of horizontal rows and vertical columns, each column representing a different sampling time interval and each row representing a different magnitude.

The waveform data sequence is processed to provide "bit nap", a stored data array indicating whether or not each pixel is to be illuminated.

In a horizontal raster scan oscilloscope, an electron beam periodically sweeps horizontally over each pixel row and the beam is turned on and off during its sweep so that pixels to be included in a waveform are illuminated while pixels not to be included in a waveform are not illuminated.

Accordingly, at any given time, a waveform display is based entirely on the waveform data sequence acquired during the last input signal sampling cycle and does not reflect any information about wave for. data acquired during earlier sampling cycles. Thus, noise has a more pronounced effect on the display in a digital oscilloscope than in an analog oscilloscope.

Summarv of the Invention A digital oscilloscope digitizes an input signal at a plurality of sampling times relative to each occurrence of a repetitive triggering event to produce sequences of waveform data ("vector lists Each vector list represents the time dependent behavior of the input signal during a separate sampling period, each element of each vector list having associated therewith a particular magnitude and a particular sampling time relative to an occurrence of the triggering event.

The oscilloscope produces on a screen a waveform display in response to the vector lists, the waveform display representing the magnitude of the input signal as a function of time by selectively illuminating pixels of an array of rows and columns of pixels on the screen. Bach row of pixels represents a separate input signal magnitude and each column of pixels represents a separate sampling time interval relative to an occurrence of the triggering event. Therefore, each pixel has associated therewith the input signal magnitude and the sampling time interval indicated by the particular row and column containing the pixel.In accordance with the invention, the intensity of each pixel of the array is an increasing function of the number of acquired vector list elements having associated therewith a magnitude substantially similar to the magnitude represented by the illuminated pixel, and having associated therewith a relative sampling time within the time interval represented by the illuminated pixel. The intensity of each pixel is also a decreasing function of tine, the number of received vector lists or the number of received vector list elements.

When the input signal is periodic, and the triggering event is appropriately chosen so that the input signal is digitized at similar points during successive sampling periods, pixels included within a waveform display representing the input signal grow increasingly brighter, up to a predetermined intensity limit. Transient noise in the input signal or in the oscilloscope itself may occasionally alter the magnitude of vector list elements so that pixels not included in the representative waveform are occasionally illuminated, but such pixels will only be dimly illuminated and will quickly fade in intensity.

Thus, the waveform display isrelatively insensitive to noise and the variable intensity of pixels included in the waveform provides information regarding behavior of the input signal over a period longer than the sampling period represented by a single vector list.

It is accordingly an object of the invention to provide an improved digital method and apparatus for displaying a waveform representing the magnitude of an analog input signal as a function of tine.

The subject matter of the present invention is particularly pointed out and distinctly claimed in the concluding portion of this specification.

However, both the organization and method of operation of the invention, together with further advan tages and objects thereof, may best be understood by reference to the following description taken in connection with accompanying drawings wherein like reference characters refer to like elements.

Brief Descrintion of the Drawina FIG. 1 is a block diagram of an oscilloscope implementing the present invention FIG. 2 is a block diagram of the display system of FIG. 1; and FIG. 3 is a block diagram of the pixel processor circuit of FIG. 2.

DescriDtion of the Preferred Embodiment FIG. 1 is a block diagram of a raster scan oscilloscope for displaying a waveform representation of an analog input signal in accordance with the present invention. The input signal is applied to a vertical preamplifier 10 which adjustably offsets, amplifies and/or attenuates the input signal. The output of vertical preamplifier 10 provides input to a digitizer 12 that digitizes an input signal ata plurality of sampling times relative to each occurrence of a repetitive triggering event in the input signal to produce sequences of waveform data ("vector lists").Each vector list represents the time dependent behavior of the input signal during a separate sampling period, each element of each vector list having associated therewith a particular magnitude and a particular sampling tine relative to an occurrence of the triggering event. The digitizer 12 transmits each vector list through a display bus 14 to a random access acquisition memory 16 for storage at sequential addresses therein, memory addressing being provided by the digitizer.

Thereafter, the vector list may be read out of acquisition memory 16 and transferred via bus 14 to a display system 18 which creates a waveform display on a cathode ray tube (CRT) screen 20 in accordance with the vector list.

A microprocessor 22, operating under instructions stored in a memory 24, controls operation of vertical preamplifier 10, digitizer 12, and display system 18 using control data transpitted thereto through a system bus 26, connecting memory 24 to the microprocessor. A user tells the microprocessor 22 how to select gain, offset, sampling rate, trigger level and other operating parameters of the vertical preamplifier 10 and digitizer 12 by operating pushbuttons and/or control knobs or other well-known input devices which cause user interface circuitry 28 to transmit suitable control input data to microprocessor 22.

Microprocessor 22 has access to display bus 14 through bus interface circuitry 30 interconnecting the display bus 14 and the system bus 26, and can access acquisition memory 16 to read, modify and/or write vector lists therein. Acquisition memory 16 can store several vector lists defining waveforms representing several previously digitized input signals, and microprocessor 22 selects vector lists to be transferred to the display system 18 in accordance with user input, thereby allowing the user to control which waveforms are displayed on screen 20.

The digitizer 12 transmits a message to the microprocessor 22 each time that it stores a vector list in acquisition memory 16. To produce a "real time" display of a waveform representing an input signal, the digitizer continuously digitizes the input signal to produce successive display lists, and microprocessor 22 quickly transfers each vector list from the acquisition memory 16 to the display system 18 so that the display system can quickly update a representative waveform display in accordance with the incoming display list.

In the preferred embodiment, the oscilloscope of FIG. 1 is a horizontal raster scan device wherein screen 20 provides a display organized into an array comprising rows and columns of pixels, each of which ray be illuminated with variable intensity. Each uccessive pixel column represents a successive time interval relative to a triggering event, and each pixel row represents a different input signal magnitude. An electron beam periodically sweeps horizontally over each pixel row, and as it sweeps, the beam's intensity is modulated so that pixels to be included in a waveform are illuminated with variable intensity.

The beam is turned off as it sweeps over pixels not included in a waveform so that such pixels are not illuminated. The determination as to whether a pixel is to be illuminated, and the determination as to the intensity of the illumination of each pixel that is to be illuminated, are made in accordance with a bit map created and stored by display system 18 in response to the input vector lists.

In the preferred embodiment, the bit nap includes 4-bit intensity data values associated with each pixel, the value of the intensity data indicating the intensity with which the associated pixel is to be illuminated. If the pixel is not to be illuminated, the intensity data has value 0000 (binary) If the pixel is to be illuminated, the 4-bit intensity data indicates one of 15 intensities numbered in order of increasing intensity from 0001 through 1111, and the display system sets the pixel intensity in accordance with the intensity data value.

Display system 18 of FIG. 1, depicted in lore detailed block diagram form in FIG. 2, comprises a frame buffer 32, including a memory that stores the bit nap, and a display controller 34 that periodically reads pixel intensity data out of the bit map and generates signals controlling the vertical and horizontal movement of the electron beam as well as its intensity. When a vector list is transmitted on bus 14 to the display system 18 from the acquisition memory 16 of FIG. 1, it is stored in a random access memory (RAM) 36. Data lines of display bus 14 are directly connected to data input terminals of RAM 36 while address lines of the display bus are indirectly connected to address terminals of RAM 36 through a multiplexer 38.

In a "raster" node of operation, vector list data elements read out of RAM 36 are provided as input to a rasterizer 40 which produces as output an array of intensity data, each element of the array corresponding to a separate pixel of the pixel array of CRT screen 2Q of FIG. 1. The intensity data array output of rasterizer 40 provides input to a pixel processor 42 which nay perform various logic operations on the intensity data to selectively adjust its value.The pixel processor 42 then transmits the adjusted intensity data to frame buffer 32 to update the bit map of the pixel array of screen 20 Microprocessor 22 of FIG. 1 controls operation of multiplexer 38, rasterizer 40, and pixel processor 42 by placing control data in control registers 44, accessed through the system bus 36, and the control data stored in registers 44 provides control input to these devices. Read/rite operation of RAM 36 and frame buffer 32, and various operations of rasterizer 40 and pixel processor 42, are timed by clock signals produced by a state machine 46 in accordance with control data provided by control registers 44.State machine 46 also provides control signals and addresses for reading data out from RAM 36 and for read and write accessing.

In the raster mode operation, the vector list is read out of RAM 36 and transmitted to rasterizer 40 several times, once for each horizontal row of pixels, and rasterizer 40 uses the vector list to determine an intensity value for each pixel on each row. Rasterizer 40 transmits data indicating the computed intensity value to pixel processor 42 and pixel processor 42 passes the intensity data to frame buffer 32 for storage at a location within the bit map associated with the pixel. State machine 46 also provides addresses and control signals to the frame buffer 32 causing it to store each intensity data value at the appropriate location in the bit nap within the frame buffer.

As previously mentioned, the display controller 34 periodically reads the bit-napped intensity data out of frame buffer 32 and produces a waveform display wherein pixels are illuminated with in intensities in accordance with the bit map data. In the raster mode of operation, a waveform display is formed by a set of vectors, each vector comprising a straight line between two endpoints on the screen at elevations representing magnitudes of two successive input signal samples, and at horizontal positions representing timing of the two samples.

Each vector is drawn on the screen by illuminating pixels having center points bounding the trajectory of the vector on the screen. Further, the intensity of each such illuminated pixel is modulated as a function of the horizontal or vertical distance of its center point (i.e., its centroid) from the vector trajectory.

Rasterizer 40 and the use of pixel intensity gradation to provide waveform displays formed by apparently continuous vectors are described and claimed in co-pending U.S. patent application entitled "Raster Scan Waveform Display with Pixel Intensity Gradation".

In a "sequential" mode of operation, microprocessor 22 of FIG. 1 transfers a vector list representing a waveform from the acquisition memory 16 to RAM 36 via bus 14, having set a bit in control registers 44 to cause multiplexer 38 to supply RAM 36 with addresses and control signals provided on display bus 14. When the vector list transfer is complete, the microprocessor changes the bit stored in control registers 44 so that multiplexer 38 thereafter supplies addresses produced by state machine 46 to RAM 36. The data output terminals of the vector list RAM 36 are also connected to inputs of state machine 46, and state machine 46 begins reading the vector list stored in RAM 36 by generating addresses and control signals for RAM 36.Each vector list includes a data element associated with each column of pixels on the screen, and that data element indicates the input signal magnitude at a relative sampling time within a time interval represented by the associated pixel column.

In the sequential mode of operation1 state machine 46 supplies a pixel data address to frame buffer 32 in response to each element of the vector list and the 16-bit pixel data that is addressed in response to each vector list element controls the intensity of four horizontally contiguous pixels on the screen. A particular one of those pixels is at a horizontal position on the screen corresponding to a sampling time interval relative to the triggering event that includes the relative sampling time associated with the vector list element. The particular pixel is at a vertical position that most nearly represents the magnitude indicated by the vector list element.

In accordance with the invention, the pixel processor 42 reads the 16-bit pixel data stored in frame buffer 32 at the address supplied by the state machine and increments the value represented by four bits of the pixel data by a predetermined amount to provide a new pixel data value. The four bits that are incremented are those which define the intensity of the particular pixel associated with the vector list element. The state machine 46 provides input to pixel processor 42 indicating which four bits are to be incremented. The state machine also provides a "pixel clock" signal to pixel processor 42 which enables the pixel processor to latch the new pixel data value onto data input terminals of the frame buffer 32 so that the new pixel data value is written into the frame buffer memory at the current address.

Thus, in the sequential mode of operation, the intensity of one particular pixel in each pixel column is incremented whenever a vector list element is supplied to the state machine 46, and the particular pixel is selected in accordance with the magnitude and relative sampling tine indicated by vector list element. Therefore, when a periodic input signal is repetitively digitized to provide a succession of substantially similar vector lists, pixels in a waveform display representing the input signal grow increasingly brighter as each vector list is processed until such pixels reach maximum intensity. The state machine 46 may also periodically address every storage location in frame buffer 32 containing pixel data, and cause the pixel processor 42 to decrement the pixel data at each address.Therefore, the intensity of each pixel is both a decreasing function of time and an increasing function of the number of vector list elements having associated therewith a magnitude substantially similar to the magnitude represented by the pixel at a relative sampling time within the tine interval represented by the pixel column containing the pixel.

Alternatively. state machine 46 nay count the number of vector lists (or vector list elements generated), and when the count reaches a predetermined limit, the state machine may address every storage location in frame buffer 32 containing pixel data, and cause the pixel processor 42 to decrement the pixel data at each address In such ease, the intensity of each pixel is both a decreasing function of number of vector list elements generated and an increasing function of the number of vector list elements having associated therewith a magnitude substantially similar to the magnitude represented by the pixel at a relative sampling time within the time interval represented by the pixel column containing the pixel.

When the input signal is periodic, and a triggering event is appropriately chosen so that the input signal is digitized at similar points along each of successive cycles, the digitizer produces vector lists at regular intervals. When the input signal remains unchanged, the vector lists are all similar and pixels included within a waveform display representing the input signal grow increasingly brighter, up to a predetermined intensity limit. However, transient noise in the input signal or in the oscilloscope itself may occasionally alter the magnitude of a vector list element so that pixels not included in the representative waveform are occasionally illuminated. But such pixels will only be dimly illuminated and will quickly fade in intensity.Thus, the waveform display is relatively insensitive to noise, and the variable intensity of pixels included in the waveform provides information regarding behavior of the input signal over a period longer than one digitizing cycle of the input signal.

The manner and amounts by which the pixel processor 42 increments and/or decrements pixel data can be controlled by microprocessor 22 of FIG.

1 by placing appropriate control data in control registers 44. For example, it may be preferable in some applications to decrement the intensity of a pixel down to a predetermined limit once the pixel has reached some minimum level of illumination so that the pixel continues to remain dimly illuminated. In this mode of operation, the system produces a bright waveform representing a periodic input signal as long as the input signal remains unchanged in frequency or magnitude. When the magnitude or frequency of the input signal suddenly changes, a new waveform is displayed and the pixels that form it quickly grow bright as the waveform is repeatedly digitized.The original waveform quickly grows dim due to the periodic decrementing of the intensities of pixels that form it, but the original waveform not does not entirely fade away because of the lower limit to which a pixel intensity may be reduced. Thus, an operator can easily compare the two waveforms to determine the nature of the sudden change to the input signal.

The pixel processor 42 may also be set to increment pixels referenced by a vector list to full intensity in a single step while decrementing all pixels in smaller steps. In n this mode of operation, the intensity of each pixel is still a function of the number of previously processed vector lists that reference the pixel, but the contributions of the most recently processed vector lists are given more weight in setting pixel intensity.Although such a mode operation provides less noise immunity in the display than when pixel intensities are gradually incremented, the waveform display is updated more rapidly following a change in the input signal because the system quickly produces a bright waveform in response to the first vector list acquired after the input signal change and does not require several digitizing cycles to incrementally increase pixel intensity.

Pixel processor 42 of FIG. 2 is shown in more detailed block diagram form in FIG. 3. With reference to FIG. 3, a multiplexer 109 can connect any one of its two 4-bit inputs to any one of a set of four registers 110. The 4-bit intensity data from rasterizer 40 of FIG. 2 provides one input to multiplexer 109 and control registers 44 of FIG. 2 provide an additional 4-bit input to multiplexer 109. As discussed hereinabove, frame buffer 32 of FIG. 2 stores bit-mapped pixel data in the form of 16-bit words, each word indicating the intensity of four horizontally contiguous pixels, and the pixel processor collects intensity data associated with four horizontally continuous pixels before performing logical operations on them.In the raster mode of operation, incoming intensity data values from the rasterizer pass through multiplexer 109 and are stored in successive ones of registers 110 on successive cycles of the pixel clock. State machine 46 of FIG. 2 counts and decodes the pixel clock to provide four sequentially asserted control signal inputs to registers 110.

In the sequential mode of operation, the data stored in the four registers 110 is supplied by the control registers 44 of FIG. 2 via multiplexer 109.

The 4-bit input to multiplexer 109 is a value indicating an amount by which pixel intensity will be increased. The data stored in each register 110 is associated with a separate one of four horizontally contiguous pixels, and the state machine 46 of FIG. 2 sets multiplexer 109 prior to input enable each register 110 so that an appropriate value is passed into each register 110.

The content of each register 110 is supplied to an A input of a separate one of four arithmetic logic units (ALUs) 112, operations of which are controlled by data from control registers 44 of FIG. 2. The 4-bit output of each ALU 112 provides input to a latch 114 that is clocked by a signal from the state machine every fourth pixel clock cycle. Latch 114 thus latches a 16-bit data word onto its output terminals every fourth pixel clock cycle, and this latched data word provides the pixel data word input to the frame buffer 32 of FIG. 2. The data word is stored in the bit map within the frame buffer at an appropriate address provided by state machine 46 of FIG. 2.

Prior to storing pixel data at a particular address in the frame buffer, the 16-bit data word currently stored at that address is read out and supplied as input to a set of four ROMs 116. Control data from control registers 44 of FIG. 2 also forms an additional part of the address inputs of ROMs 116. Each ROM 116 is programmed to produce a 4-bit intensity data value output supplied to the B input of a corresponding ALU 112, and the ALUs combine their A and B inputs in a manner determined by their control data inputs to provide their intensity data outputs to latch 114. Depending on the value of address input data from the control registers, ROMs 116 may, for example, provide outputs that are equal to their intensity data value address inputs from the frame buffer or that may be less than such inputs by a predetermined amount. ROMs 116 may also set their outputs to 0000 or other predetermined values regardless of the value of input intensity data from the frame buffer. Also depending on control data supplied by registers 44 of FIG. 2, each ALU may selectively pass only its A input, pass the maximum of its A and B inputs, pass only its B input, add with saturation its A and B inputs, OR or XOR (exclusive OR) its A and B inputs, set its output to 1111 or 0000, or perform other logic or arithmetic operations on its A and/or B inputs to produce an output.

When the system operates in the raster mode, the intensity data at the A inputs of ALUs 112 are supplied by the rasterizer and ALUs 112 are set to pass their A inputs to latch 114 without change.

In such case, the intensity of a particular pixel on the screen is a function of its vertical or horizontal distance from one or two vectors forming a waveform as determined by the intensity data produced by the rasterizer in response to a vector list. To overlay several waveforms on the screen, ROMs 116 may be set to produce output data equal to their input data and ALUs 112 may be set to XOR or sum their A and B inputs.

On the other hand, when the system is operating in the sequential mode in accordance with the present invention, the intensity of each pixel may selectively be a decreasing function of time (or number of vector lists or vector list elements processed) and an increasing function of the number of acquired vector list elements representing a magnitude approximately equal to the magnitude represented by the pixel row containing the pixel at a relative sampling time within the relative sampling time interval represented by the pixel column containing the pixel. When a vector list is processed,. data provided by control registers 44 sets ALUs 112 to sum their A and B inputs and sets ROMs 116 to pass their inputs unchanged to the B inputs of the ALUs.

The data supplied to the A input of each ALU 112 has a value determined by data supplied to multiplexer 109 from control registers 44 of FIG.

2. This value determines the amount by which pixel data in the frame buffer memory is increased when a vector list element indicates that an associated pixel is to be included in a waveform. To periodically decrement each pixel data value in the frame buffer, the state machine periodically sets the content of the control register so that ALUs 112 pass their B inputs unchanged and so that each ROM 116 produces an output that is a selectively a linearly or non-linearly decreasing function of its intensity data address input.

Although a waveform display provided in the sequential mode of operation may have a less smooth appearance than a display produced in the raster mode of operation, the sequential mode waveform display is relatively less sensitive to noise and the variable intensity of pixels provides information regarding behavior of the input signal over a period longer than the single sampling cycle represented by a single vector list.

While a preferred embodiment of the present invention has been shown and described, it will be apparent to those skilled in the art that many changes and modifications may be made without departing from the invention in its broader aspects.

The appended claims are therefore intended to cover all such changes and modifications as fall within the true spirit and scope of the invention

Claims (18)

Claims

1. An apparatus for producing a waveform display representing an input signal, comprising: an array of pixels, each pixel having a position within the array representing a different combination of magnitude of the input signal and time interval relative to an occurrence of a repetitive trigging event in the input signal; digitizing means responsive to the input signal for sequentially generating data elements, each data element indicating an input signal magnitude at a different sampling time relative to a repetitive triggering event in the input signal; and display control means for receiving the data elements generated by said digitizing means and for illuminating pixels of the array with variable intensity in response to received data elements such that an intensity of an illuminated pixel is an increasing function of a number of data elements received that represent a magnitude substantially similar to the magnitude represented by the illuminated pixel at a sampling time within the time interval represented by the illuminated pixel.

2. The apparatus in accordance with claim 1 wherein the intensity of the pixel is also a decreasing function of a number of data elements received by said display control means.

3. The apparatus in accordance with claim 1 wherein the intensity of the pixel is also a decreasing function of a time.

4. An apparatus for producing a waveform display representing an input signal, comprising: an array of pixels, each pixel having a position within the array representing a unique combination of input signal data; digitizing means responsive to the input signal for sequentially generating digital data elements, each data element having a magnitude; and display control means for receiving data elements generated by said digitizing means and for illuminating pixels of said array with independently adjustable intensities in response to received data elements, an intensity of a pixel illuminated with less than a predetermined maximum intensity being increased whenever a data element representing its unique position is received, and intensities of all pixels illuminated with more than a predetermined minimum intensity being periodically decreased.

5. The apparatus in accordance with claim 4 wherein said display control means comprises: frame buffer means for storing and reading out pixel data values, each pixel data value corresponding to at least one pixel of said array and indicating an intensity of said pixel; pixel processing means for receiving a pixel data value read out of said frame buffer means, for selectively either incrementing or decrementing the read out pixel data value to produce a new pixel data value, selection being made in accordance with control signals provided as input to said pixel processing means, said pixel processing means supplying the new pixel data value to said frame buffer means for storage therein;; means for receiving data elements from said digitizing means and for causing said frame buffer means to read out to said pixel processing means the pixel data value corresponding to said at least one pixel whenever a received data element indicates a combination of input signal magnitude and time such that the input signal magnitude is substantially similar to the magnitude represented by the illuminated pixel at a sampling time within the time interval represented by said at least one pixel, and for causing said frame buffer means to store the new pixel data value produced by said pixel processing means; and means for illuminating pixels of said array to intensities indicated by corresponding pixel data values stored in said frame buffer means.

6. An apparatus for producing a waveform display representing an input signal, comprising: an array of pixels, each pixel having a position within the array representing a unique combination of magnitude and time interval relative to a repetitive triggering event in the input signal; digitizing means for generating vector lists by digitizing the input signal, each vector list comprising a sequence of data elements, each data element indicating a magnitude of the input signal at a particular time relative to an occurrence of a repetitive event, the magnitude being indicated by a value of the data element and the particular time being indicated by a position of the data element within the sequence; and display control means for receiving the vector lists generated by said digitizing means and for illuminating pixels of said array with variable intensities such that an intensity of each illuminated pixel is an increasing function of a number of received vector list data elements that indicate an input signal magnitude substantially similar to the magnitude represented by the illuminated pixel at a sampling time within the time interval represented by the illuminated pixel.

7. The apparatus in accordance with claim 6 wherein the illumination intensity of each pixel is also a decreasing function of time.

8. The apparatus in accordance with claim 6 wherein the intensity of the pixel is also a decreasing function of a number of data elements received by said display control means.

9. A method for producing a waveform display representing an input signal, the display being produced on an array of pixels, each pixel having a position within the array representing a different combination input data, the method comprising the steps of: generating digital data elements characterizing said input signal. each indicating a said combination of input data; and adjusting illumination intensities of pixels of the array such that intensity of each illuminated pixel is an increasing function of a number of data elements indicating the same combination of input data.

10. The method in accordance with claim 9 further comprising the step of periodically decreasing the illumination intensity of each illuminated pixel so that intensity of each pixel is a decreasing function of time.

11. The method in accordance with claim 9 further comprising the step of periodically decreasing the illumination intensity of each illuminated pixel so that intensity of each pixel is a decreasing function of a number of data elements generated.

12. A method for producing a waveform display representing an input signal utilizing an array of pixels, each pixel having a position within the array representing a unique combination of input signal magnitude and time interval relative to a repetitive triggering event in the input signal, the method comprising the steps of: generating a sequence of data elements, each data element representing a magnitude of the input signal and a'time relative to an occurrence of the repetitive event at which the input signal had the magnitude; and illuminating pixels of said array with independently adjustable intensities such that intensities of pixels illuminated with less than a predetermined maximum intensity are increased whenever one of said data elements represents an input signal magnitude substantially similar to the magnitude represented by the illuminatedspixel at a sampling time within the time interval represented by the illuminated pixel, and such that intensities of pixels illuminated with more than a predetermined minimum intensity are periodically decreased by a predetermined amount.

13. The method in accordance with claim 12 wherein the step of illuminating pixels comprises the substeps of: periodically adjusting pixels of said array to illumination intensities indicated by corresponding pixel data values stored in memory means; reading out of the memory means a pixel data value corresponding to a pixel of said array whenever a generated data element indicates an input signal magnitude substantially similar to the magnitude represented by the illuminated pixel at a sampling time within the time interval represented by the illuminated pixel; incrementing the read out pixel data value to produce a new pixel data value; and storing the new pixel data value in the memory means memory in place of said read out pixel data value.

14. The method in accordance with claim 13 wherein the step of illuminating pixels further comprises the substep of periodically decrementing the pixel data values stored in said memory means.

15. A method for producing a waveform display representing an input signal utilizing an array of pixels, each pixel having a position within the array representing a unique combination of magnitude and time interval relative to an occurrence of a triggering event in the input signal, the method comprising the steps of: generating vector lists by successively digitizing an input signal, each vector list comprising a sequence of data elements, each data element indicating a magnitude of the input signal at a particular time relative to an occurrence of the triggering event, the magnitude being indicated by a value of the data element and the particular time being indicated by a position of the data element within the sequence; and illuminating pixels of said array with variable intensities such that an intensity of each illuminated pixel is a function of time and of a number of received vector list data elements that indicate an input signal magnitude substantially similar to the magnitude represented by the illuminated pixel at a sampling time within the time interval represented by the illuminated pixel.

16. A method for producing a waveform display representing an input signal utilizing an array of pixels, each pixel having a position within the array representing a unique combination of magnitude and time interval relative to an occurrence of a triggering event in the input signal, the method comprising the steps of: generating vector lists by successively digitizing an input signal, each vector list comprising a sequence of data elements, each data element indicating a magnitude of the input signal at a particular time relative to an occurrence of the triggering event, the magnitude being indicated by a value of the data element and the particular time being indicated by a position of the data element within the sequence; and illuminating pixels of said array with variable intensities such that an intensity of each illuminated pixel is a decreasing function of a total number of vector lists generated and an increasing function of a number of received vector list data elements that indicate an input signal magnitude substantially similar to the magnitude represented by the illuminated pixel at a sampling time within the time interval represented by the illuminated pixel.

17. An apparatus for producing a waveform display representing; an input signal substantially as hereinbefore described with reference to the accompanying drawings.

18. A method for producing a waveform display representing an input signal substantially as hereinbefore described.