US 4,829,293 A · Method and apparatus for achieving variable and infinite persistence

Abstract

Method and apparatus for achieving unlimited and variable presistence in a digital oscilloscope having a samplier, analog-to-digital converter, high speed memory, microprocessor, linked list memory, display memory with bits corresponding to pixels on a raster display screen and hardware for refreshing the screen from memory. Variable persistence controls the length of time waveform data persists on a display. Waveform data persists indefinitely with unlimited persistance. For unlimited persistence, analog data is acquired by the sampler, converted to digital, stored in high speed memory, converted to coordinates corresponding to appropriate pixels, and corresponding display memory bits are set. For variable persistence, linked lists are maintained for each column on the display screen, each link containing a row coordinate and time remaining before erasing variable. Acquired data is converted to coordinates, lists are searched, new links from a spare links pool are added to the lists for new points, and time remaining variables are reset for old points. Time remaining variables are decremented at intervals, links are removed from the lists and returned to the spare links pool when time remaining variables reach zero, and corresponding bits in display memory are cleared. Persistence is shortened when memory approaches overflow conditions. Lookup tables are used for determining row coordinates. Additional waveforms and graticule may be stored in display memory and displayed on the display screen at an intensity perceptibly different from the live waveform intensity.

Claims20

Dependent claims

A method of achieving unlimited persistence of waveforms on a raster display screen for a digital oscilloscope comprising the steps of:

(1) acquiring analog data from a signal in a system under test,
(2) converting said analog data to digital data,
(3) storing said digital data in a high speed memory,
(4) setting bits in a display memory which correspond to pixels on said raster display screen, according to said digital data in said high speed memory,
(5) refreshing said raster display screen continuously from said display memory whereby said refreshing occurs independently of steps (1) through (4),
(6) repeating steps (1) through (4) sequentially without clearing said display memory until stopped by a first user command whereby all said bits set in said display memory remain set until cleared by a second user command.

3 more elements

A method of achieving variable persistence of waveforms on a raster display screen for a digital oscilloscope comprising the steps of:

(1) initializing linked lists and a pool of spare links in a display memory for maintaining a first set of point location data and a first set of time remaining data corresponding to said first set of point location data,
(2) acquiring analog data from a signal in a system under
(3) converting said analog data to digital data,
(4) storing said digital data in a high speed memory, then,
(5) decrementing time remaining datum in said first set of time remaining data in said linked lists, then,
(6) removing links having time remaining datum less than or equal to zero from said first set of said time remaining data in said linked lists, and placing said links in said pool of spare links, then,
(7) converting said digital data to a second set of point location data, then,
(8) updating time remaining datum for links in said linked lists having point location datum substantially equal point location datum in said second set of point location data, then,
(9) adding links to said linked lists from said pool of spare links for each point location datum in said second set of point location data not currently in a link in said linked lists, then,
(10) setting bits in a second display memory according to said second set of point location data, then,
(11) refreshing said raster display screen continuously from said second display memory,
(12) repeating step (2) through step (10) sequentially until stopped by a user command,

9 more elements

Apparatus for implementing unlimited persistence or variable persistence in a digital oscilloscope, comprising:

sample means for sampling and holding analog data from a signal in a system under test,
converter means connected to said sampler means for converting said analog data to digital data,
first memory means connected to said converter means for storing said digital data,
second memory means for storing linked lists having point location data and time remaining data,
third memory means having storage locations for storing display states for a set of display points as defined by locations of points corresponding to point location data currently in said linked lists,
display means connected to said third memory means having specific display points corresponding to said storage locations in said third memory means for displaying points according to said display states of said third memory means,
microprocessor means connected to said first memory means, said second memory means, and said third memory means responsive to a user command selecting variable or unlimited persistence mode for creating, updating and maintaining said linked lists in variable persistence mode and for converting said digital data to corresponding display states in said third memory means in unlimited persistence mode.

4 more elements

Dependencies are inferred from the claim text.

Method and apparatus for achieving variable and infinite persistence

Life of this patent

Method and apparatus for achieving variable and infinite persistence

Life of this patent

Abstract

Claims20