| 摘要 |
PURPOSE:To enable an operator to confirm immediately the effectiveness of operation of a light pen, by setting an interruption flip-flop by the output of an effectiveness checking part and transmitting an interruption signal and at the same time by ringing a buzzer with the output of the flip-flop. CONSTITUTION:An effectiveness checking part 18 is newly added to confirm the effectiveness of the position information of a light pen that is written to a light pen register 15. Then an interruption flip-flop 17 is set by the output of the part 18. The confirmation of effectiveness is possible by confirming that the coincidence is obtained among the values stored in the register 15 through several times of scanning and that the stored value is smaller than the prescribed value for both the line and character positions. As a result, it is prevented that the wrong position information is read into a host device owing to an inaccurate operation of a light pen. |
