Key output method for keyboards

Claim 1

A method of controlling the issuance of keyboard signals from a keyboard system having a matrix of rows and columns of lines which can be electrically interconnected by a corresponding key at each intersection of the rows and columns, the system also having a memory with a plurality of memory locations each corresponding to a respective key, said method comprising the steps of: (1) detecting whether two keys of said keyboard system are concurrently depressed by determining the number of flags in said memory, each of said flags being an indication in a memory location that a particular key is currently being depressed, each memory location being associated with a predetermined key; (2) upon detection in step 1 of two keys not being concurrently depressed, detecting whether a key has been newly depressed since the detecting step of step 1; (2a) upon detection in step 2 of a key being newly depressed, setting a flag in a memory location associated with said key being newly depressed and issuing a key code representing said key being newly depressed; (2b) upon detection in step 2 of no key being newly depressed, returning to step 1; (3) upon detection in step 1 of two keys being concurrently depressed, detecting whether a key has been newly depressed since the detecting step of step 1; (3a) upon detection in step 3 of a key being newly depressed, setting a flag in a memory location associated with said key being newly depressed and determining, by checking flagged memory locations, whether a condition exists which gives rise to a false indication of a key depression; (3b) upon determination in step 3a that said condition giving rise to a false indication of a key depression does exist, returning to step 1 without issuing a key code representing said key detected as being newly depressed in step 3; (3c) upon determination in step 3a that said condition-giving rise to a false indication of a key depression does not exist, issuing a key code representing said key detected as being newly depressed in step 3; and (3d) upon detection in step 3 of no key being newly depressed, returning to step 1.

Claim 2

A method of controlling the issuance of keyboard signals from a keyboard system having a matrix of rows and columns of lines which can be electrically interconnected by a corresponding key at each intersection of the rows and columns, the system also having a memory with a plurality of memory locations each corresponding to a respective key, said method comprising the steps of: (1) detecting whether two keys of said keyboard system are concurrently depressed by determining the number of flags in said memory, each of said flags being an indication in a memory location that a particular key is currently being depressed, each memory location being associated with a predetermined key; (2) upon detection in step 1 of two keys not being concurrently depressed, detecting whether a key has been newly depressed since the detecting step of step 1; (2a) upon detection in step 2 of a key being newly depressed, setting a flag in a memory location associated with said key being newly depressed and issuing a key code representing said key being newly depressed; (2b) upon detection in step 2 of no key being newly depressed, returning to step 1; (3) upon detection in step 1 of two keys being concurrently depressed, detecting whether a key has been newly depressed since the detecting step of step 1; (3a) upon detection in step 3 of a key being newly depressed, setting a flag in a memory location associated with said key being newly depressed and determining, by checking flagged memory locations, whether a condition exists which gives rise to a false indication of a key depression; (3b) upon determination in step 3a that said condition giving rise to a false indication of a key depression does exist, returning to step 1 without issuing a key code representing said key detected as being newly depressed in step 3; (3c) upon determination in step 3a that said condition-giving rise to a false indication of a key depression does not exist, issuing a key code representing said key detected as being newly depressed in step 3; and (3d) upon detection in step 3 of no key being newly depressed, returning to step 1.