Claims
- 1. A data input apparatus comprising:
- (a) a key switch device, including:
- a first group of lines extending parallel to one another;
- a second group of lines extending parallel to one another and intersecting with the lines of the first group;
- a plurality of key switches for connecting the lines of the first group to the lines of the second group, each of said key switches being located at a respective intersection of a line of the first group and a line of the second group;
- a serial circuit comprising a plurality of first resistors connected in series, each of said first resistors being connected in parallel between adjacent lines of the second group; and
- a second resistor, and a constant-voltage source connected through said second resistor to one end of said serial circuit at a connecting point; and
- (b) a processing apparatus, including:
- pulse-supplying means for supplying a periodic pulse to each line of said first group, the pulses being supplied to different lines at different times; and
- detector means coupled to said pulse-supplying means and to the connecting point for detecting a potential at the connecting point and, in accordance with said potential and with the times at which pulses have been supplied to the lines of said first group from said pulse supplying means, for determining which key switch has been operated.
- 2. The apparatus according to claim 1, wherein said pulse-supplying means includes a low-level pulse supplying means for holding the lines of said first group in a normally open condition and for supplying periodic low-level pulses to these lines, the pulses supplied to different lines at different times.
- 3. The apparatus according to claim 2, wherein said low-level pulse supplying means includes:
- a plurality of switching means for holding said lines of said first group in said normally open condition and for periodically connecting these lines to a ground, said switching means each connected to a respective line of said first group; and
- switch control means for causing said switching means to periodically connect each of the lines of said first group to the ground, the connecting of different lines to ground being at different times.
- 4. The apparatus according to claim 3, wherein said switching means, said switch control means, and said detector means are formed as a single large-scale integration circuit.
- 5. The apparatus according to claim 4, wherein said detector means includes:
- potential-comparison means for comparing the potential at the connecting point with a reference voltage which level incrementally changes, and for outputting a comparison result; and
- key-detecting unit for detecting, in accordance with the comparison result and the times at which said switch control means causes said switching means to connect said lines of the first group to the ground, which key switch has been operated.
- 6. The apparatus according to claim 5, wherein said switch control means and said detector means are formed as a single large-scale integration circuit.
- 7. The apparatus according to claim 1, wherein said detector means includes:
- potential-comparison means for comparing the potential at the connecting point with a reference voltage which level incrementally changes, and for outputting a comparison result; and
- key-detecting unit for detecting, in accordance with the comparison result and the times at which said switch control means causes said switching means to connect said lines of the first group to the ground, which key switch has been operated.
Priority Claims (1)
Number |
Date |
Country |
Kind |
63-12008 |
Jan 1988 |
JPX |
|
Parent Case Info
This is a continuation of application Ser. No. 298,750, filed on Jan. 19, 1989, which was abandoned upon the filing hereof.
US Referenced Citations (9)
Foreign Referenced Citations (3)
Number |
Date |
Country |
3340749 |
Nov 1983 |
DEX |
35226 |
Feb 1984 |
JPX |
154533 |
Sep 1984 |
JPX |
Non-Patent Literature Citations (1)
Entry |
Halbleiter-Schaltungstechnik, Springer-Verlag Berlin Heidelberg, New York 1978, pp. 568-575. |
Continuations (1)
|
Number |
Date |
Country |
Parent |
298750 |
Jan 1989 |
|