Claims
- 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.
- 2. The method of claim 1, wherein said keyboard is connected to a central processing unit for detecting when said keys are depressed, said central processing unit including a random-access memory for storing said flags corresponding to respective keys in said keyboard.
Priority Claims (1)
Number |
Date |
Country |
Kind |
59-153784 |
Jul 1984 |
JPX |
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Parent Case Info
This application is a continuation of application Ser. No. 07/081,529, filed Aug. 3, 1987, which is a continuation of application Ser. No. 06/758,523, filed July 24, 1985, now abandoned.
US Referenced Citations (6)
Foreign Referenced Citations (2)
Number |
Date |
Country |
0089646 |
Sep 1983 |
EPX |
0122928 |
Sep 1979 |
JPX |
Non-Patent Literature Citations (2)
Entry |
Bland and Bolt, "Phantom Key Detection/Phantom Key Scan Code", IBM Technical Disclosure Bulletin, vol. 27, No. 7A, Dec. 1984. |
"Solution to Phantom Key Problems", IBM Technical Disclosure Bulletin, vol. 28, No. 5, Oct. 1985. |
Continuations (2)
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Number |
Date |
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Parent |
81529 |
Aug 1987 |
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Parent |
758523 |
Jul 1985 |
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