CRT TOUCH SWITCH INPUT DEVICE

摘要

PURPOSE:To eliminate a detection error by accepting no input of a detection circuit for contact of a touch switch for a flyback period when the induced voltage obtained through the screen scan of a CRT is kept at a high level. CONSTITUTION:The synchronizing signal of a CRT 7 if delivered in a waiting mode of touch switch input is supplied to a CPU 4 in the form of an interruption of high priority. Then an input terminal is masked to invalidate the detection for time T1 during which the position detecting voltage is affected by the induced voltage. Thus the detected value is not accepted in an output period of the synchronizing signal during which the detected value is not accurate. Then the detected value is accepted in other periods. Thus a contact position is detected accurately.