JPS62169223A - Key input circuit - Google Patents

Abstract

PURPOSE:To reduce the number of pins of a control IC by connecting N-number of sets of keys, each of which consists of M-number of keys, to N-number of input/output terminals of a key matrix circuit. CONSTITUTION:A control circuit (IC) 11 consisting of a microcomputer or the like in a key input circuit is provided with N-number of (for example, three) input/output terminals 21-23, and output terminals of output circuits 24-26 and input terminals of input circuits 27-29 are connected to them. The IC 11 detects the key input state on a basis of data contents from input circuits 27-29 and controls a device body. The key matrix circuit is provided with sets of diodes D1 and keys K1 and K2 correspondingly to terminals 21-23. One terminal out of three terminals 21-23 is controlled to the low or high level output state and the other terminals are controlled to the high impedance output state to detect a signal corresponding to the level state of each terminal as an input signal.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a key input circuit, and particularly to a key input circuit that can connect many keys with a small number of terminals.

[Technical Background of the Invention] In recent years, the functions of electronic devices have improved. For example, in television receivers, users used to adjust the volume using a rotary or sliding variable resistor, but now the operability has improved. It's starting to change to nice soft-touch controls. Another example is that although conventional television receivers only reproduced television broadcasts through cathode ray tubes and speakers,
Nowadays, it is common to have a built-in function to input and play other video and audio signals, and these signals can also be selected using soft-touch keys.
Operation is now controlled by key human input signals.

In such a system, in order to control the circuit operation of an electronic device according to the user's wishes, keys are arranged on the main body of the electronic device, and the user touches a pre-specified key to achieve his/her purpose. Inside an electronic device, it is necessary to assign functions to each key on the main body of the electronic device and to detect the touch of the knee, but this also consists of an electronic circuit, and an integrated control circuit such as a microcomputer. It is now held in

By the way, when detecting information using multiple keys with the above integrated circuit (hereinafter referred to as control IC), if the number of keys is m (m is an integer), control IC usually A common terminal to which one end of the base key is connected and m input terminals to which the other end of each key is connected are required. However, this is not preferable because if the number of keys increases, the number of IC terminals must also increase, and there is a limit to the number of IC terminals.

Therefore, a circuit as shown in FIG. 2 has been conventionally used. The circuit shown in FIG. 2 will be explained below.

In FIG. 2, 1 is a control IC, and this IC 1 has a signal deriving bin 2.3 as a common terminal,
Input bins 4 and 5°6 are provided as input terminals, and output terminals of output circuits 7 and 8 that generate high level J5 and low level signals are connected to the signal deriving bins 2 and 3, respectively. The input terminals of input circuits 9, 10.11 for introducing the bin input information into the internal circuit are connected to the bins 4.5.6.

The signal deriving bin 3 has three keys Kl, 2, and 3.
are connected to one end of each of the keys and have a 1°K2. The other ends of 3 are connected to input bins 4.5.6, respectively.

In addition, the signal derivation bin 2 has 4. to 5
．． are connected to one end of each of the 6 and 4 to these keys. 5.
The other ends of 5 and 6 are respectively connected to input bins 4 and 5.6. Note that input bins 4, 5, and 6 are connected to resistors R1 and R2, respectively.
It is connected to the reference potential point via R3.

Table 1 shows the operation of the circuit as described above.

Table 1 In this Table 1, A and B indicate signals derived to the signal derivation bin 3.2, H is a high level, and L is a low level. According to Table 1, when signal @A is high level and signal B is low level, it is possible to detect the conduction state of 1 to 3 in the key. For example, if 1 is conductive to the key, the signal is input to bin 4. becomes high level, and the control ICI learns from the signal from the input circuit 9 that 1 has been operated on the key.

Also, if signal A is at low level and signal B is at high level, and 4 is conductive to the key, it can be determined that 4 is conductive to the key based on the high level signal to bin 4. . Thus A=H, B=L or A=L, B=H
It is possible to detect which key has been operated based on the logical state of the key and the state of the key.

[Problems with Background Art] The conventional circuit constitutes a time-division detection type key input circuit in which when the terminal B is at the "H" level, the terminal B is at the "L" level, or vice versa. Five control IC bins are required to obtain the human power for six keys.This number can be smaller than the seven bins required when time-sharing detection is not performed, but the number of keys increases and, for example, When 12 keys are required, a minimum of 7 bins are required even if the number of signal derivation bins is 3, and there is a problem that the number of connections between the key input circuit and the control IC increases. While microcontrollers are required to be mounted on the surface of electronic equipment, microcontrollers are often installed inside the equipment, and when wiring between them, the large number of connections complicates the structure and increases noise. This has the disadvantage of causing a decline in performance, such as being more easily affected by

[Object of the Invention] The present invention has been made in view of the above-mentioned points, and an object of the present invention is to provide a key input circuit that can reduce the number of control TC bins required for detecting human key force compared to the conventional one. It goes off.

[Summary of the invention 1 N sets of M keys (M<N) are connected to N terminals (N is a positive integer and N>1) for both input and output provided in a control circuit. One end of each key is connected to the corresponding terminal in common, and the other end of each key of each set is connected to another terminal different from the terminal to which one end of the key is connected, and N This is a key input circuit that controls one of the terminals to a high or low level output state and the other terminals to a high impedance output state, and detects a signal according to the level state of each terminal as input data. .

[Embodiment 1 of the invention Hereinafter, the present invention will be described with reference to illustrated embodiments.

FIG. 1 is a circuit diagram showing an embodiment of a key input circuit according to the present invention.

In FIG. 1, numeral 11 is an integrated control circuit (hereinafter referred to as control IC) using a microcomputer, etc., and this IC 11 has N terminals, for example, three terminals 21, 22, and 23, which are used for both input and output. (N is a positive integer and N>1). And these terminals 21~
23 are connected to the output terminals of output circuits 24, 25, and 26 and the input terminals of input circuits 27, 28, and 29, respectively. The output circuits 24, 25, 26 output control signals L1. By supplying III, the electrical state of the output terminal can be switched between a high or low level signal state and a high impedance state. When in a high impedance state, the input circuits 27 and 28
．． 29 is supplied with the signals appearing at terminals 21, 22, and 23 as key manual data. Control IC11
detects the state of key manual operation based on the data contents from these input circuits 27, 28, and 29, and further controls the main body of the device.

Each terminal 21, 22, 23 has a resistor R11, R1, respectively.
2, connected to the reference potential point (earth) via R13, and reverse current blocking diodes D1. D2.
It is connected to each anode of D3.

Next, regarding the key matrix circuit, the cathode of the diode D1 is commonly connected to one end of each of the two keys at 1°K2, and each key is connected to 1°K2. The other ends of 2 are connected to terminals 22 and 23, respectively. Also, the cathode of diode D2 is connected to the key 3. are commonly connected to one end of each of 4 and 3 to each key. The other ends of 4 are connected to terminals 21. and 4, respectively.
23, and the cathode of diode D3 is connected to key 5. are connected to one end of each of keys 5 and 6, and the other ends of keys 5 and 6 are connected to terminals 21 and 22, respectively. In other words,
Each key [1 (K1. to 2 set, K3゜K4 set, K5
．． 6 sets) are provided corresponding to the terminals 21, 22, and 23, respectively, and one end of each set of keys is commonly connected to each corresponding terminal, and the other ends of each set of keys are not in a corresponding relationship. Each terminal is connected to one of the other terminals.

The present embodiment is configured as described above, and its operation will be explained next.

Table 2 shows the performance clothing of the embodiment shown in FIG. In this table, Ql, Q2. Q3 indicates the output state of the output circuits 24, 25, and 26, H indicates a state in which a high level signal is output, and Q1z indicates a high impedance state.

Table 2 As is clear from Table 2, the circuit of FIG.

Q2. It detects which of keys 1 to 6 is turned on in a time-sharing manner among three states (1) to (3) in which any one of Q3 exhibits a high level signal.

(1) When Ql=H, Q2=l-12, Q3=H2,
When Ql exhibits a high level, terminal 21 transmits a high level signal to key Kl via diode D1.

Lead to group K2. Therefore, at this time Kl.

If one of K2 is turned on, a high level signal appears at either terminal 22 or 23. As a result, for example, when the key is set to 1, a high level signal appears at the terminal 22, and this signal is supplied to the control IC 11 through the input circuit 28, so that the control IC 11 recognizes that the key is set to 1. can be detected. In this case, since the output state of the output circuit 25 is a high impedance state, the input circuit 28 guides the signal from the terminal 22 to the output side. Incidentally, when the key 2 is turned on, the signal at the terminal 23 becomes high level, and the human force applied to the key 2 can be detected.

(2) Ql = H2, Q2 = H, Q3 = H2 (71)!
-! In this case, a high level signal appears at the terminal 22, and the other terminals 21 and 23 become high impedance. Therefore, the key is 3. If either one of 4 is turned on, the signal appearing at terminals 21 and 23 becomes high level, and the key 3. This enables manual detection of four sets of keys.

(3) Q1=H2, Q2-4-17. Q3=H(7),
! : In this case, a high level signal appears at the terminal 23, and the other terminals 21 and 22 become high impedance. Therefore, for example, when K5 is on, the signal to terminal 21 is high level, and when K6 is on, the signal to terminal 22 is high level,
5 on the key. 6 sets of keys can be manually detected.

The right column of Table 2 shows the above.

In this way, in this embodiment, by supplying a signal to one terminal and turning on any key arranged corresponding to this terminal, the state of the signal appearing at the other terminal can be changed. Key human power can be detected by reading the signal status. Therefore, the three terminals 21, 22, 23
Despite this, it is possible to detect 1 to 6 key human forces on 6 keys. This is 11 out of N terminals.
[! a, and detect the on state of the key connected to N terminals based on whether the signal appears at the remaining N-1 terminals, and NX(N-1) The key to human detection is now possible. Therefore, when four terminals are provided, inputs from a maximum of 12 keys can be detected.

Incidentally, in the above embodiment, the output circuits 24 and 25 are used as means for controlling the electrical state of the terminals to which signals are supplied via the keys.
．． 26 is constructed with 31i11 output elements, but the present invention is not limited to this means. Also, output circuit 24.25.26
Although an example has been described in which the output state of the key is switched to ``to 1'' or high impedance, it is also possible to read the key manual state by switching between low level ``L11'' and high impedance.

[Effects of the Invention] As explained above, according to the present invention, when configuring a key matrix circuit, the number of terminals and the number of connections can be significantly reduced, and when the number of terminals is N, the maximum (N=1) keys can be connected. Furthermore, since the number of connections can be reduced, chances of noise intrusion are reduced, which has the effect of reducing malfunctions and element deterioration due to noise.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram showing an embodiment of a key input circuit according to the present invention, and FIG. 2 is a circuit diagram showing an example of a conventional key input circuit. 11...Control ■C1 21, 22, 23...IC terminals, 24.25.26...Output circuit, 27.28.29...Input circuit, K1. 2. 3...key.

Claims (1)

[Scope of Claims] A control circuit having N terminals (N is a positive integer and N>1) for both input and output; or a circuit for switching between a first state exhibiting a low level and a second state exhibiting a high impedance, the circuit switching when any one of the N terminals is in the first state. an output circuit that causes the other terminals to enter a second state; an input circuit that is included in the control circuit and is supplied with a signal corresponding to the level state of each of the terminals as input data; N sets of keys each having M keys (M<N) are provided corresponding to the respective terminals, one end of each set of keys is connected to each corresponding terminal in common, and
A key input circuit comprising: a key matrix circuit in which each other end of each set of keys is connected to a terminal different from the terminal to which one end of the set is connected.