SELF-TUNING DIGITIZER CONTROL CIRCUIT AND METHOD

A digitizer control circuit (10) is disclosed which employs a tunable digitizer-screen energizing source (16,18,20). In addition, the digitizer control circuit includes a stylus (24) for sensing the energizing signal, and a circuit (30) for processing the information signal from the stylus (24), including a narrow bandpass filter (48) for passing the frequency of the energizing signal and minimizing the passage of extraneous noise. A controller (14) determines the location of the stylus (24) on the active surface of the energized digitizer screen (22) and controls operation of the circuit. The energized source includes a tunable divide-by-n circuit (16) employing an 8-bit latch (54), an 8-bit counter (56), and a state machine (58). A nonvolatile memory (34) stores the most recent value for the divisor value n.