| 摘要 |
PURPOSE:To obtain the useful key input device which can realize many key inputs with less terminal numbers, by providing the tristate output circuit generating a tri-state output, and the key input circuit having the function of tri-state discrimination at another end of the key matrix. CONSTITUTION:Six phase clocks i-Vi are obtained with a poly-phase clock generator 12 and they are fed to AND gates 13a-13l, and also to tri-state output circuits 14A-14C. When a clock is fed to the input terminal 15, it is inverted at the inverter 16 to turn on the transistor 17. The output from the output terminal 18 is at high level. When a clock is fed to the input terminal 19, the transistor 20 is ON, and the output from the output terminal 18 is at low level. If pulses are not input to any of the input terminals 15, 19, transistors 17, 20 are OFF, and a voltage divided with resistors 21, 22 is output at the output terminal 18. |
