Coded data generation or conversion – Bodily actuated code generator – Including keyboard or keypad
Patent
1991-09-27
1993-11-23
Yusko, Donald J.
Coded data generation or conversion
Bodily actuated code generator
Including keyboard or keypad
341 24, 341 25, H03M 1120
Patent
active
052648451
ABSTRACT:
A key scan circuit and the method thereof in a microcomputer is disclosed which requires no diode for preventing circuit short and performs key check or automatic operations with a simplified circuit structure. The key scan method includes a step of designating the input/output mode of a bilateral port by a data direction register in a microcomputer which includes an input/output bilateral port and an input only unilateral port, so as to prevent circuit shorts when more than one key are pushed. Further, by using first and second memories, the key scan method includes a step of determining whether the number of logic low states in the first memory is greater than one, and determining whether the number of logic high states stored in the second memory is greater than one, thus indicating the pressing of multiple keys. Then, the pushed key's value is determined by a predetermined formula by obtaining the value m when the mth bit value of the first memory is logic low, and the value n when the nth bit value of the second memory is logic high.
REFERENCES:
patent: 4231016 (1980-10-01), Ueda
patent: 5059974 (1991-10-01), Wu
Kim Hyeon-su
Kwon Sun-don
Bushnell Robert E.
Horabik Michael
Samsung Electronics Co,. Ltd.
Yusko Donald J.
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