C language functions for millisecond timing on the IBM PC

Dlhopolsky, Joseph G.

doi:10.3758/bf03203909

Cited by 17 publications

(14 citation statements)

References 11 publications

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“…Dlhopolsky (1988) made the same modifications in the C language. Creeger, Miller, and Paredes (1990) suggested emulating the standard system timer interrupt, so that the time of day clock would not run at a higher rate.…”

Section: Hauss Mannmentioning

confidence: 99%

Tachistoscopic presentation and millisecond timing on the IBM PC/XT/AT and PS/2: A Turbo Pascal unit to provide general-purpose routines for CGA, Hercules, EGA, and VGA monitors

Haussmann

1992

Behavior Research Methods, Instruments, & Computers

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A review of the literature on adopting microcomputers for use in tachistoscopic research paradigms illustrates the need for a comprehensive package to effectively deal with the wide variety of video displays and microcomputers used in experimental settings. In addition, because of the large number of possible configurations created when video displays and computer systems are combined, there is a need to be able to efficiently drive any such combination without rewriting program code. A Turbo Pascal unit is presented to provide standard tachistoscopic routines compatible with monochrome, eGA, Hercules, EGA, and VGA video technology. Procedures that synchronize both text and graphics mode stimuli with the vertical retrace pulse are given, as are routines to provide access to a timer with better than millisecond precision. Pascal code is described that will run on the IBM PC, XT, AT, or PS/2, as well as on any compatible machine. The versatility of the unit allows the experimenter to use generic video and timer commands that will automatically adapt at run time to the system that is being used, without further experimenter intervention.As microcomputer technology increases at an evergrowing rate, prices of powerful system configurations continue to drop. Complete workstations boasting clock speeds of 33 MHz, extended resolution monitors, and hard disk storage on the order of 200 MB are available for less than $2,000. Yet although many researchers use such systems daily for word processing and statistical analysis, many do not utilize the machines' full capabilities. These systems can be employed as fully automated data collection devices, and the researcher who addresses a few of the limitations of the hardware can thus use the microcomputer in many behavioral research settings.This material is based upon work supported under a National Science Foundation Graduate Fellowship. The author would like to thank Ed Domber and Janet Davis for guidance in the project from which this work is an offshoot. Special thanks also to Bethann Lefsky for comments on earlier drafts, and to the anonymous reviewers for their helpful suggestions on a preliminary version of this article. Correspondence should be addressed to Robert E. Haussmann, Department of Psychology, P.O. Box llA Yale Station, New Haven, CT 06520-7447. Controlling Stimulus OnsetThe attempt to use a microcomputer to generate visual stimuli with millisecond precision raises several technical issues, the most important of which consists of the limitations of the video display hardware. VGA (video graphics array) displays are capable of presenting images at great resolution (up to 1,024 X 640 pixels). When one considers, however, how the information moves from the computer to the display, one discovers that several possible problems can arise in the attempt to accurately control short-duration stimuli.A video display operates much as a common television set does. In the case of a color monitor, three electron beams rapidly scan the entire screen, from left to right on e...

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Section: Hauss Mannmentioning

confidence: 99%

Tachistoscopic presentation and millisecond timing on the IBM PC/XT/AT and PS/2: A Turbo Pascal unit to provide general-purpose routines for CGA, Hercules, EGA, and VGA monitors

Haussmann

1992

Behavior Research Methods, Instruments, & Computers

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“…The ZERO_TIMER macro sets the timer to O. These macros, together with the two functions, seUimer() and reseUimer() (lines 012-026), have been described elsewhere (Dlhopolsky, 1988). They constitute the millisecond timer.…”

Section: Program Descriptionmentioning

confidence: 99%

Synchronizing stimulus displays with millisecond timer software for the IBM PC

Dlhopolsky

1989

Behavior Research Methods, Instruments, & Computers

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A C language technique for synchronizing millisecond timer software to the appearance of the stimulus on the IBM PC's video monitor is described. Tachistoscopic programs that use the technique can correct the mean 8.3-msec bias normally found in reported response latencies and reduce the associated error variance.Researchers considering the use of the IBM PC for tachistoscopic applications should know that the appearance of a stimulus on the video monitor is controlled by two asynchronous processes: the computer program and the video display circuitry. The program executes instructions that result in the storage of character data (or pixel images) in random access memory (RAM) that is dedicated to the video display. The display processing hardware recurrently reads video RAM and controls the intensity of the monitor's electron beam as it "draws" images. The result: the computer program-which also initiates the timing of response latencies-normally does not know the precise moment at which the display process causes the stimulus to appear on the screen.The decoupling of the program and video processes has a number of effects of interest to researchers who require precise control over brief stimulus displays and millisecond interval timing. As the vertical dimension of the stimulus increases, it becomes more likely that the stimulus will be drawn on the screen in parts. For example, the electron beam might be aimed at the middle of the screen when the program transfers the stimulus data to video RAM. The bottom portion of the stimulus would then appear first, followed by an interval during which the electron beam would be scanning the bottom and then the top of the screen (both areas presumably empty of stimulus parts). Finally, the top portion of the stimulus would appear. The interval between the appearance of first-and last-drawn portions would be 16.7 msec (assuming a monitor with a 6O-Hz refresh frequency).The situation for response latencies produces both biased results and increased error variance. If the program starts a millisecond timer following the execution of the commands to display the stimulus, the timer will have been running an average of 8.3 msec before the stimulus Correspondence may be addressed to Joseph G.

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“…Furthermore, channel 2 of the timer chip can be used as a real-time timer, programmable to count at almost any rate between about 20 Hz and 2 MHz. The programming is essentially the same as that for channel 0 on the same 8253 or 8254 chip, but users of timing routines on channel 2 need not worry about disturbing the IBM BIOS realtime clock, as must those using channel 0 (see Dlhopolsky, 1988;Emerson, 1988).…”

mentioning

confidence: 99%

Book review of DOS 5: A developer’s guide

Emerson

1992

Behavior Research Methods, Instruments, & Computers

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C language functions for millisecond timing on the IBM PC

Cited by 17 publications

References 11 publications

Tachistoscopic presentation and millisecond timing on the IBM PC/XT/AT and PS/2: A Turbo Pascal unit to provide general-purpose routines for CGA, Hercules, EGA, and VGA monitors

Tachistoscopic presentation and millisecond timing on the IBM PC/XT/AT and PS/2: A Turbo Pascal unit to provide general-purpose routines for CGA, Hercules, EGA, and VGA monitors

Synchronizing stimulus displays with millisecond timer software for the IBM PC

Book review of DOS 5: A developer’s guide

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