Patent ID: 7965280

Claim:
Touch screen controller circuitry comprising: a host processor; a touch screen assembly having first and second resistive screens and having a first, second, and third terminals; pen touch detection circuitry for providing a pen touch detection signal having a first level if a touch point of touch screen assembly is detected, wherein the pen touch detection circuitry includes: a first transistor that is coupled to a first terminal of the touch screen assembly at its source; a second transistor that receives a first reference voltage at its source and that is coupled to a second terminal of the touch screen assembly at its drain; a third transistor that receives a second reference voltage at its source and that is coupled to a third terminal of the touch screen assembly at its drain a buffer that is coupled to the drain of the first transistor, wherein the buffer generates a pen touch detection signal; a pull-up resistor that is coupled to the drain of the first transistor, wherein a resistance of the pull-up resistor is substantially greater than a total resistance through the first and second resistive sheets, the touch point, and the third transistor coupled between the second reference voltage and the source of the first transistor to thereby cause the first level of the pen touch detection signal to be a low voltage and a second level of the pen touch detection signal to be a high voltage; and a control circuit for receiving the pen touch detection signal and for receiving a convert command from the host processor and operative to produce an interrupt signal to be sent to the host processor in response to the pen touch detection signal if the first level is received, and operative to reset the interrupt signal in response to the pen touch detection signal if the second level is received before the convert command is received from the host processor, the interrupt signal representing an interrupt service request for the convert command, wherein resetting of the interrupt signal cancels the interrupt service request.