LIGHT PEN

PURPOSE:To prevent the transfer of incorrect position through the high accuracy and precision of input position detection, by providing a counter counting a pulse at the period having an acceptance signal at each scanning, latches and a comparison circuit. CONSTITUTION:Latches 2, 5 are cleared with the leading of a pen touch signal PT. A counter 4 is cleared at a horizontal synchronizing signal HD, the signal PT and a spot accepting signal LA are ANDed at an AND gate 6, its output and the LSB of a horizontal address HA are ANDed at a gate 3, and its output counts up the counter 4. A comparison circuit 7 compares the output of the counter 4 with an output of the latch 5 latching the maximum count value of the counter 4, and when the former is larger, the compared output 1 is given to the latches 2 and 5. The maximum period information where the accpeting signal LA is 1 is stored in the latch 5 with the signal and the position information of the time is stored in the latch 2.