Patent ID: 6650317
Filing Date: 2003-11-18
Classification: G06F,G09G

Abstract:
An electronic system for preventing malfunction of key switch encoding comprising:A. key switches, each having a quiescent state to block a signal from passing through the key switch and an information entry state to pass a signal through the key switch for entering information into the system; B. memory circuits containing instruction words for operating the system; and C. a single monolithic integrated semiconductor including the memory circuits, which include read only memory containing the instruction words, processor circuits, output terminals and input terminals, the output terminals being separate from the input terminals and the terminals being coupled to the key switches, the output terminals carrying sequences of active state output signals coupled to the key switches and the input terminals carrying input, signals occurring in response to the active state output signals passing through key switches in an information entry state, the output and input signals effecting a scanning of the key switches that is subject to malfunction, the processor circuits being coupled to the terminals and to the memory circuits and the processor circuits operating the system in response to executing the instruction words, the system including prevent means for preventing malfunction of the key switch scanning by executing at least one instruction word that results in a delay before distinguishing a key switch in an information entry state from a malfunction, and the system including defeat means for defeating double key entry after completing an operation by detecting the states of the key switches through the terminals to determine whether some key switch is still in the information entry state, and, if so, then waiting a length of time by executing at least one instruction word and again detecting the states of the key switches through the terminals until a condition is detected that no key switch is in an information entry state before again responding to any key switch being in an information entry state.