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980 DP 1.4 Video Generator / Analyzer - User Guide
16.134
Persist
16.134.1
Description
In the primary version, 15 small white boxes move back and forth between diagonal guide lines. The lines form 15
side-by-side tracks. The size of each box is scaled to the light meter box size set by the MSIZ system parameter.
The image does the following:
•
The box in the center track (marked "1X") moves one scan line vertically and one pixel horizontally for each
vertical frame of refresh.
•
The seven boxes to the right of the center track (marked "2X" through "8X") move 2, 3,4, 5, 6, 7, and 8
pixels and lines per frame, respectively.
•
The seven boxes to the left of the center track (marked "/2" through "/8") move one scan line vertically and
one pixel horizontally for every 2, 3, 4, 5, 6, 7, and 8 vertical frames of refresh, respectively. These boxes
are at the bottom of the tracks.
In cases where the next move would cause the box to move beyond the end of its track, it immediately reverses
and moves the correct distance in the opposite direction for the next frame.
A continuously-running counter appears in the upper left corner of the image. The number shown is the number of
vertical frame refreshes that have occurred since the generator was first powered up.
The secondary version draws a black image on a white background.
An example of the primary version of the Persist image is shown below:
16.134.2
Test
Phosphor persistence
16.134.3
Purpose
The phosphors on the face of most CRTs continue to glow for a short period of time after the electron beam has
stopped energizing them. This phenomenon is called persistence. A certain amount of persistence is desirable in
Page 450
Rev. A1
June 16, 2017
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