| 摘要 |
PURPOSE:To detect a light pen less than a character unit on a CRT monitor by providing a counter which generates clocks obtained by dividing the synchronizing clocks of a CRT controller. CONSTITUTION:A light pen address latch (AL) 14 inputs a refresh memory address transmitted from a CRT display controller (CRTC) 6 through a latch 15a for synchronizing, an ADRS SET signal obtained by processing a light pen detection signal in an interface signal process circuit 10 and the basic clock CRTC 101, the half CRTC clock 102 and the quarter CRTC clock of the CRTC 6 generated in a counter 16 which generates the synchronizing basic clock of the CRTC 6. Thus, the AL 14 can detect eight signals from three CRTC clocks and detect the character by one-eighth width of the character.
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