JP2828787B2 - Key input circuit and telephone integrated circuit having key input circuit - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a key input circuit capable of inputting either a single-contact key switch or a two-contact key switch, and more particularly to a key input circuit built in a telephone integrated circuit. .

[0002]

2. Description of the Related Art In general, a dialer (an integrated circuit for outputting a dial pulse or a dial tone) used in a push-button telephone is provided with a key input circuit to which a keyboard is connected. The keyboard used for the push button type telephone has a single contact type key switch as shown in FIGS.
Some use a contact type key switch. That is, FIG.
Has a single-contact switch that is short-circuited by operating a key at each intersection of a row line and a column line. On the other hand, in the keyboard of FIG. 3, switches are arranged between a row line and a column line and a predetermined voltage, for example, a ground voltage. When a key is operated, each switch of a row and a column corresponding to the key, that is,
The two contacts are short-circuited.

A key input circuit using the keyboard shown in FIG. 2 sequentially outputs H level to a column line, inputs a low line signal to each of them, and determines an operated key switch. After the H-level is output and the L-level is output to the column line, a low-line signal change is input, and then the H-level is output to the column line and the L-level is output to the low line, thereby outputting the column line signal. There is a method of determining a key operated by inputting a change.

A key input circuit using the keyboard shown in FIG. 3 outputs an H level to a row line and a column line, and determines a key operated by inputting a signal change of the row line and the column line. In order to reduce power consumption, the telephone integrated circuit using the keyboard shown in FIG. 2 or 3 starts oscillating when it detects that a key has been operated, and performs processing corresponding to the key input by starting oscillating. After the termination, the oscillation is stopped again to enter the standby state.

[0005]

As described above, the conventional integrated circuit for telephones stops oscillation in the standby state. However, in this standby state, oscillation starts when any key on the keyboard is operated. , A key input operation is performed. That is, even when a function key, for example, a key other than a telephone number registration mode key or an on-hook dial key, for example, a numeric key is operated, oscillation starts, and a key input operation is performed. In this case, only the input operation of the numeric keys is performed, and no substantial operation such as a dial operation corresponding to the numeric keys is performed. That is, useless key input operation is performed, and useless power is consumed.

[0006]

SUMMARY OF THE INVENTION The present invention has been made in view of the above points, and a keyboard in which a single-contact key switch and a two-contact key switch are arranged in a row and a column is connected. In a possible key input circuit,
A row input terminal, a column input terminal, impedance means connected between each of the row input terminal and the column input terminal and a first potential, and a second input terminal connected to each of the row input terminal and the column input terminal. Switching means connected between potentials; input gate means connected to each of the row input terminal and the column input terminal; switching means and the input gate means connected to the row input terminal; and the column input terminal A gate means for supplying a key scan signal of opposite phase to the switching means and the input gate means, respectively, and a prohibition signal for controlling the gate means and prohibiting the supply of the key scan signal. The key input of the single contact key switch of the keyboard is invalidated by the generation of the inhibit signal, and only the key input of the two contact key switch is provided. By enabling, prohibits the key input operation by the operation other than the required key, is intended to reduce the power consumption.

[0007]

According to the above means, when the inhibit signal is generated in the standby state, the key scan signal is not output from the gate means, and the switching means and the input gate connected to the row input terminal and the column input terminal are turned off, Since the row input terminal and the column input terminal are fixed to the first potential by the impedance means, the potential of the row input terminal and the column input terminal does not change even if a single contact key switch is operated, and Although the operation is invalidated, when the two-contact key switch is operated, the terminal potentials of the row input terminal and the column input terminal transition to the second potential, and the key operation is detected.

[0008]

FIG. 1 is a circuit diagram showing an embodiment of the present invention, and shows a case of an integrated circuit for a push-button telephone. In the figure, a keyboard 1 has single contact key switches 2 and 2
A single contact key switch 2 corresponds to a numeric key or the like, and has two contact key switches 3.
Corresponds to a function key such as a key for setting a telephone number storage mode. 2 One end of the contact of the contact key switch 3 is grounded and the other each row lines R ₁ to R ₄
And column lines C _{1 to} C ₄ . The low lines R _{1 to} R ₄ and the column lines C ₁ to
C ₄ is connected to the row input terminals R _{IN1 to} R _IN4 and the column input terminals C _{IN1 to} C _IN4 of the integrated circuit 4, respectively.

In the integrated circuit 4, the low input terminal R _IN1
To R _IN4 and column input terminals C _{IN1 to} C _IN4 and power supply voltage V
_An impedance element 5 serving as a pull-up resistor is connected between _DD and an N-channel MOS transistor 6 between the row input terminals R _{IN1 to} R _IN4 and the column input terminals C _{IN1 to} C _IN4 and the ground voltage. Is connected. Also, row input terminals R _{IN1 to} R _IN4 and column input terminals C _{IN1 to} C _IN4
Is connected to one input of a NOR gate 7 which is an input gate. Further, the gate electrode of the MOS transistor 5 connected to the low input terminals R _{IN1 to} R _IN4 and the NOR gate 7
The other input is connected to the output of an AND gate 8 in common, and is connected to a column input terminal C _{IN1 to} C _IN4.
The output of the AND gate 9 is commonly connected to the gate electrode of the transistor 5 and the other input of the NOR gate 7.
The AND gates 8 and 9 are prohibition gates that output the key scan signals SKC and * SKC having phases opposite to each other. The key scan signal SKC is applied from the clock generation circuit 10 to the AND gate 8, and the AND gate 9 is The signal * SKC inverted by the inverter 11 is applied. Further, the inhibit signal SKINH output from the control circuit 12 is commonly applied to the AND gates 8 and 9.

The output of the NOR gate 7 is connected to a latch input of a latch circuit 13 controlled by a latch clock LCK output from the clock generation circuit 10, and outputs a low signal indicating an operated key position on the keyboard 1. The column data is latched by the latch circuit 13. The output of the latch circuit 13 is applied to a key decoder 14 for creating a key code corresponding to each key of the keyboard 1. The key code output of the key decoder 14 is applied to the control circuit 12. The control circuit 12 controls an internal circuit (not shown) in order to realize the function in accordance with the applied key code, and outputs a control signal OSCSTOP for stopping the oscillation of the oscillation circuit 15 after the control is completed. When the device enters the standby state, it outputs a prohibition signal SKINH. The oscillation of the oscillation circuit 15 starts at the low input terminal R
_{IN1 to RIN4} are controlled by the output of the NAND gate 16 connected to the input. That is, the low input terminals R _{IN1 to} R _IN
When the voltage at any one point of _IN4 becomes the ground voltage, the oscillation of the oscillation circuit 15 starts. The oscillation output of the oscillation circuit 15 is used as a signal source for the clock generation circuit 10 to generate a clock signal such as the latch clock LCK and the key scan signal SKC.

Next, the operation of the circuit diagram shown in FIG. 1 will be described. First, in the standby state, the inhibition signal SKI
When NH is at the ground voltage, that is, at L level, AN
The outputs of the D gates 8 and 9 both become L level. As a result, all the MOS transistors 5 are turned off. Therefore, the row input terminals R _{IN1 to} R _IN4 and the column input terminal C
_IN1 to _CIN4 are raised by the impedance element 5 to the power supply voltage, that is, the H level. In this state, even if the single contact key switch 2 is operated and the contacts are short-circuited,
Since the row line and the column line are at the same H level, the row input terminals R _{IN1 to} R _IN4 and the column input terminal C
The voltage levels of _IN1 to _CIN4 do not change at all. Therefore, N
The output of the AND gate 16 is at L level, and the oscillation circuit 1
5, the key operation of the single-contact key switch 2 is completely ignored.

On the other hand, when the two-contact key switch 3 is operated, only one of the row lines and one of the column lines to which the operated key switches are connected are lowered to L level by the key switch, and the row input terminal R _{One of IN1 to} R _IN4 becomes L level. As a result, the NAND gate 16
Becomes H level, and the oscillation of the oscillation circuit 15 starts. The control circuit 12 sets the inhibit signal SKINH to the H level by the output of the NAND gate 16.

When the oscillation starts, the clock generation circuit 10
Output the key scan signal SKC and the latch clock LCK in synchronization with each other. First, the key scan signal SKC
Is at the L level, the output of the AND gate 8 is at the L level and the output of the AND gate 9 is at the H level, so that the MOS transistors 6 of the low input terminals R _{IN1 to} R _IN4 are at the low level.
Is off, and the signals of the low input terminals R _{IN1 to} R _IN4 are NO
Through R gate 7 is inverted is supplied to the latch circuit 13, whereas, MOS transistor 6 of the column input terminal C _IN1 -C _IN4 is turned on, the signal of the column input terminal C _IN1 -C _IN4 is pulled down to the L level However, since the output of the AND gate 9 is at the H level, the column input terminals C _IN1 to C _{IN1 to} C
The outputs of the NOR gate 7 of _IN4 are all at L level. Since the latch clock LCK is output in this state, the low input terminal R which has been lowered to the L level by the key operation.
_The H level is latched only in the latch circuits 13 corresponding to _{IN1 to RIN4} . The L level is latched in the latch circuits 13 of the column input terminals C _{IN1 to} C _IN4 . The row information latched by the latch circuits 13 of the row input terminals R _{IN1 to} R _IN4 is output to the key decoder and stored.

Next, the key scan signal KSC goes high.
Then, the state is reversed. That is, the low input terminal
R_IN1~ R_IN4MOS transistors 6 are all turned on and
ー Input terminal R_IN1~ R_IN4Voltage to L level,
Also, the column input terminal C_IN1~ C_IN4MOS Transistors
All the switches 6 are turned off. Therefore, the low input terminal R_IN1~ R
_IN4All outputs of the NOR gate 7 become L level,
Ram input terminal C_IN1~ C _IN4The output of the NOR gate 7 is
Only the column corresponding to the key operated column has the H level.
Become. Therefore, the NOR clock is generated by the latch clock LCK.
The output of port 7 is latched. And the column input terminal
C_IN1~ C_IN4The column information latched in the key decoder
14 and stored. The key decoder 14 stores
The key operated based on the row information and column information
A code is generated and output to the control circuit 12.

Since the two-contact key switch 3 is a function key, the control circuit 12 controls each circuit to realize a function specified by the key. Usually, the function specified by the function key is, for example,
As in the telephone number registration mode, the user must enter a numeric key until the function is completed. Therefore, the control circuit 12
When the respective circuits are controlled in order to realize the function by inputting a key code, a standby state for inputting numeric keys is set. That is, the control circuit 12 outputs the inhibition signal SKI
While holding NH at the H level, the control signal OSCSTOP is output, and the oscillation of the oscillation circuit 15 is stopped.

The key scan signal SKC output from the clock generation circuit 10 when the oscillation of the oscillation circuit 15 is stopped is
It becomes L level. Thus, the output of the AND gate 8 becomes L level, the output of the AND gate 9 to become H level, MOS transistor 6 of the low input terminal R _IN1 to R _IN4 is turned off, the low input terminal R _IN1 to R _IN4 The voltage is raised to the H level, while the column input terminals C _IN1 -C _IN
The MOS transistor 6 of _IN4 is turned on, and the voltages of the column input terminals C _{IN1 to} C _IN4 are reduced to L level. In this state, all the row lines are at the H level and all the column lines are at the L level. Therefore, when any one of the single contact key switches 2 is operated, the row line and the column line connected to the operated key switch are short-circuited. Then, one of the low input terminals R _{IN1 to} R _IN4 becomes L level. As a result, the output of the NAND gate 16 becomes H level, and the oscillation of the oscillation circuit 15 is restarted. The key code of the key operated by the same operation as described above is stored in the control circuit 12.
It is supplied to.

Finally, when a key for terminating the function (which can be the key operated for executing the function first) is operated, the key code is changed to the control circuit 12 by the same key input operation. Is applied to Then, after performing control for terminating all functions, the control circuit 12 sets the inhibition signal SKINH to L level and outputs the control signal OSCSTOP. As a result, the oscillation circuit 15 stops oscillating, and the integrated circuit 4 enters a standby state. In this standby state, the key operation of the single contact key switch 2 is ignored as described above.

The two-contact key switch 3 can be replaced by two diodes 17 and a single-contact key switch 18 as shown in FIG. In this case, since a single contact key switch with a low unit price can be used, there is an advantage that the overall cost can be reduced.

[0019]

As described above, according to the present invention, in the standby state, only the operation of the two-contact key switch is valid, and the operation of the single-contact key switch is ignored. Thus, there is an advantage that unnecessary operation due to is eliminated and power consumption can be further reduced. In particular, when used in a telephone integrated circuit, it has a great effect on reducing the power consumption of a telephone that obtains power from the telephone line, and is effective in preventing a drop in telephone line voltage due to a rapidly increasing push-button telephone. It is a target.

[Brief description of the drawings]

FIG. 1 is a circuit block diagram showing an embodiment of the present invention.

FIG. 2 is a diagram showing a keyboard using a single contact key switch.

FIG. 3 is a diagram showing a keyboard using a two-contact key switch.

FIG. 4 is a diagram showing a circuit equivalent to a two-contact key switch.

[Explanation of symbols]

 Reference Signs List 1 keyboard 2 single-contact key switch 3 2-contact key switch 4 integrated circuit 5 impedance element 6 MOS transistor 7 NOR gate 8, 9 AND gate 10 clock generation circuit 11 inverter 12 control circuit 13 latch circuit 14 key decoder 15 oscillation circuit 16 NAND Gate 17 Diode 18 Single contact key switch

Claims (3)

(57) [Claims] 1. A key input circuit to which a keyboard in which a single-contact key switch and a two-contact key switch are mixedly arranged in a row and a column is connectable, a row input terminal, a column input terminal, and the row input terminal. And impedance means connected between each of the column input terminals and a first potential; switching means connected between each of the row input terminal and the column input terminal and a second potential; and the row input terminal And input gate means connected to each of the column input terminals; the switching means and the input gate means connected to the row input terminal; and the switching means and the input gate means connected to the column input terminal. Gate means for supplying a reverse phase key scan signal, and controlling the gate means to inhibit supply of the key scan signal. A key input circuit, wherein the key input circuit disables the key input of the single contact key switch of the keyboard and enables only the key input of the two contact key switch by generating the prohibition signal. 2. When the keyboard is operated, an oscillation for generating the key scan signal is started.
A key operation detecting means connected to the row input terminal or the column input terminal, wherein only the operation of the two-contact key switch is detected by the key operation detecting means when the inhibit signal is generated. Key input circuit. 3. An integrated circuit for a telephone to which a keyboard in which a single contact key switch and a two contact key switch are mixedly arranged in a row and a column is connectable, a row input terminal, a column input terminal, and the row input terminal. An impedance means connected between each of the terminal and the column input terminal and a first potential; a switching means connected between each of the row input terminal and the column input terminal and a second potential; Input gate means connected to each of the terminal and the column input terminal, a key code decoder for creating a key code from the row and column input information input by the input gate means, and an output from the key code decoder A control circuit for controlling an operation corresponding to the key code, the switching means connected to the low input terminal, Gate means for supplying opposite-phase key scan signals to the switching means and the input gate means connected to the input gate means and the column input terminal, and the control circuit for controlling the gate means And a prohibition signal for prohibiting the supply of the key scan signal. The generation of the prohibition signal invalidates the key input of the single contact key switch of the keyboard and enables only the key input of the two contact key switch. An integrated circuit for a telephone.