Patent attributes
A key switch matrix circuit includes key switches arranged in rows and columns, each row having a scan line, each column having a sense line. Each key switch is operable to couple a scan line to a sense line. A scan signal delivery circuit supplies scan signals to the scan lines, the scan signals delivering a scan pulse to each row of the key switch matrix circuit in turn. A key switch detection circuit outputs a first signal if a key switch is operated and a scan pulse detection circuit outputs a second signal if a scan pulse is coupled to a sense line. The scan signal delivery circuit begins supplying scan signals in response to the first signal and stops supplying scan signals in response to the second signal. In one embodiment, a processor reads the sense lines in response to the second signal.
