| 摘要 |
<p>PURPOSE:To eliminate the noises which are produced when a liquid crystal element is driven and to ensure the normal detection of coordinates, by detecting the tablet coordinates after a fixed period from the rise and fall time points of a liquid crystal drive waveform AC transforming signal. CONSTITUTION:The liquid crystal drive waveform AC transforming signal delivered from a display control circuit 4 is supplied to a delay circuit 12 and an EX-OR circuit 13. The circuit 12 delays said transforming signal by a time set previously. An exclusive OR is secured between the delayed signal (a) and an undelayed signal and supplied to a tablet control circuit 11. Then an X can circuit 7, a Y scan circuit 8 and a coordinate detecting circuit 9 are controlled via the circuit 11 synchronously with an exclusive OR signal, i.e., a signal (b). The tablet coordinates can be detected by the circuit 9 when a coordinate 6 indicates a tablet 5.</p> |
