PICTURE_DRAWING_LIGHT_PEN

Published:2009/7/5 21:54:00 Author:May | From:SeekIC

Circuit improves ability to draw pictures on display screen with light pen by using short data lockout period to avoid smearing. Value of R1 depends on light pen; use 1 megohm for Texas lnstruments H-35. One-shot No. 1 produces constant-amplitude 200-ns pulse for storing 1 or 0 bit in 2102 memory of CRO graphics interface, One-shot No. 2 delays generation of another write command 0.25 s, giving operator time to withdraw or move pen before double dot is formed. R4 and C1 control length of writepulse, while R5 and C2 control wait time.-S. S.Loomis, Let There Be Light Pens, BYTE, Jan.1976, p 26-30.



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