Patent ID: 6438699
Filing Date: 2002-08-20
Classification: G06F,H03M,Y02D

Abstract:
A data processing system keyboard, comprising:a processor; a key matrix; sense lines with a pull-up value controlled by the processor; a key matrix drive circuit, having a value addressable by the processor, coupled to drive lines coupled to the key matrix; a plurality of diodes each coupled to a specified one of the drive lines; and a signal line coupled between the plurality of diodes and the processor, wherein the processor includes circuitry for testing the key matrix, wherein the key matrix drive circuit includes a common input that is coupled to all of the drive lines connected to the key matrix drive circuit and which is selectable by the processor to drive an asserted value onto one of the drive lines at a time which is then driven through one of the diodes to the signal line, and, wherein the testing circuitry includes circuitry for then scanning all drive lines coupled to the key matrix drive circuit to determine which portion of the key matrix drive circuit causes the asserted value on the signal to become negated.