Key discrimination circuit

Details Key discrimination circuit Key discrimination circuit

G - Physics

06

F

340/181

G06F 3/02 (2006.01) H03M 11/20 (2006.01)

Patent

CA 1114920

KEY DISCRIMINATION CIRCUIT ABSTRACT OF THE DISCLOSURE A key discrimination circuit comprises key switches on cross points between key input signal lines and key out- put signal lines, 2-input OR gates having output terminals which are connected to said key input signal lines and having input terminals which are connected to a 1st R-S flip-flop and 1st key discrimination signal input terminals, a 2nd OR gate having an output terminal which is connected to the 1st key discrimination output terminal and having input terminals which are connected to said key output signal lines, and AND gates having input terminals which are connected to said key out signal lines and having output terminals which are con- nected to a 3rd OR gate having an output terminal which is connected to a 2nd key discrimination signal output terminal. A key discrimination procedure is separated into two steps with to reduce noise. The 1st step is to detect that anyone of key switches is pushed, using the 1st R-S flip-flop which has the output of "1" level and the 2nd OR gate. The 2nd step is to discriminate which key is pushed, scanning key switches. By adding a further 2nd R-S flip-flop to the above described circuit, continuous key discrimination to a specific key is done noiselessly. - 0 - 0 -

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