JPS6324706Y2 - - Google Patents

Description

[Detailed explanation of the invention] This invention is based on the first line group and the second line group externally attached to the IC.
The present invention relates to an operation display of the IC in a circuit device in which a key switch is provided at each intersection of a group of lines, and the key switch selectively connects the intersection.

FIG. 1 shows a conventional circuit device, taking as an example an IC 1 for a remote control transmitter of a television receiver (the IC has a power input terminal 18 and a ground terminal 19). 11 to 18 are first line groups L1 to L connected to the key input terminals I1 to I8 of the IC1.
4 is a second line group connected to the key output terminals φ1 to φ4; 2 is a matrix key switch device in which key switches S1 to S32 are arranged at each intersection of the first line group and the second line group. When any key switch is pressed, the high level state of the key output terminals φ1 to φ4 is sequentially transferred to the first line group l1 to l8.
The line connected by the pressed key switch periodically becomes high level, and the other
The line group remains at a low level. Such key inputs are encoded within IC1 and pulse modulate the carrier. The pulse modulation signal is applied from the output terminal O to the base of an external drive transistor 3, turning on and off the transistor 3 and driving the infrared light emitting diodes 4 and 5 in accordance with the signal. 6
is a mode changeover switch, and the amount of information provided by key switches S1 to S32 is changed depending on whether the switch 6 is turned on and terminal 7 is held in the grounded state or the switch 6 is turned off and held at the power supply voltage (Vcc). It can be set twice as much as when there is no. 8 is a battery for power supply.

In such a circuit device, conventionally, when one of the key switches is pressed, an oscillator for carrier generation operates, and an external circuit 12 (terminals 16, 17) is connected to the ceramic filter 9, which is the resonator, and the capacitors 10, 11. By applying the voltage at this point to the transistor 14 via the current limiting resistor 13, the light-emitting diode 15 inserted between the collector and the battery 8 is activated. It was designed to display the operation of IC1 by driving it.

However, in the case where the voltage generated in the oscillation circuit is used in this way, it is not preferable because it causes the frequency stability of the oscillation circuit to be impaired.

Furthermore, the number of display parts is large, leading to an increase in costs.

The present invention proposes a circuit device devised to eliminate the above drawbacks without providing a dedicated terminal on the IC for driving display light emitting diodes. do.

FIG. 2 shows an embodiment of the present invention, in which the light emitting diode 15 for indicating the operation of the IC1 is
It is connected to the key output terminal φ1 of No. 1. That is, the cathode of the light emitting diode 15 is coupled to the key output terminal φ1 via the line L1, and the anode is connected to the battery 8 via the current limiting resistor 20.

Light emitting diode 15 when connected like this
In order to understand the operation of IC1, FIG. 3 also shows the internal configuration of IC1.

In FIG. 3, 21 is a key input terminal I1 to I
The encoder 21 is a key-in encoder that produces a 5-bit coded output according to the input contents of the encoder 21, and the output of this encoder 21 is registered in an instruction decoder 22 at the next stage. While this instruction decoder 22 is receiving a signal from the key-in encoder 21 (therefore, while the key switch is being pressed), the instruction decoder 22 receives a signal from the oscillation circuit 25.
A signal for driving the oscillation circuit 25 is applied to the oscillation circuit 25.
The output of the oscillation circuit 25 (frequency 455KHz) is divided by the next-stage frequency divider 26 into a 1/10 45.5KHz carrier and a lower frequency clock, and the carrier is used for timing generation. The clock signal is applied to the modulation circuit 27 via the circuit 23, and the clock signal is applied to the instruction decoder 22 and the scan signal generation circuit 24 via the timing generation circuit 23.
supplied to The output of the scan signal generation circuit 24 is at the key output terminal φ before the clock signal is applied.
1 to φ4 are all in a high level state, but are temporarily set to a low level state (t0 to t1 in FIG. 4) by the first clock signal portion,
Thereafter, the high level is sequentially transferred to the output terminals φ1 to φ4. The modulation circuit 27 pulse-modulates the carrier supplied through the timing generation circuit 23 using the code signal from the instruction decoder 22. This pulse modulated wave is led out to the output terminal O via the buffer circuit 28. 3
Reference numeral 1 denotes a mode check circuit which detects whether the level state of the terminal 7 is high or low by the mode changeover switch 6, and changes the code of the instruction decoder 22 accordingly to increase the information content handled. 29 is a current absorption circuit for allowing the current flowing through the light emitting diode 15 to flow because the display light emitting diode 15 is connected between the key output terminal φ1 and the battery 8, and the current flowing through the light emitting diode 15 generates a scan signal. Prevent it from flowing to the circuit 24 side. For completeness, it is recommended to add a diode 30 inside the IC 1 as shown in the figure. The current absorbing circuit 29 is controlled by the scan signal generating circuit 24 so that it is turned on only when the key output terminal φ1 is at a low level, and its input terminal is at a low level, and at other times, it is at a high level. If this current absorption circuit 29
If the input terminal of remains low level, the output terminal φ
1 is always at a low level, causing information errors. In FIG. 3, 31 is a mode check circuit, which is connected to an external switch 6 via a terminal 7.

Next, the operations shown in FIGS. 2 and 3 will be explained. When none of the key switches is pressed and is inactive, the key output terminals φ1 to φ4 are all at a high level [before t0 in FIG. 4], so no forward bias is applied to the display light emitting diode 15. The light emitting diode 15 is off. Next, when one of the key switches is pressed, a high level signal is transmitted to the corresponding key input terminal among the key input terminals I1 to I8, depending on the pressed key switch.
Accordingly, an operating voltage is sent from the instruction decoder to the oscillation circuit 25, so that the oscillation circuit 25 starts operating. At this time, the instruction decoder 2 is sent from the timing generation circuit 23.
A clock pulse is applied to the scan signal generating circuit 2 and the scan signal generating circuit 24, and all outputs of the scan signal generating circuit 24 are temporarily brought to a low level. In Fig. 4, the time t0 to t1 corresponds to this, and is approximately 10 msec.
It is. Subsequently, the key output terminals φ1 to φ4 are in a high level state sequentially, and accordingly, when the key output terminal φ1 is at a high level, the light emitting diode 15 is in the off state from t1 to t2, t5 to t6, . . . , t0-t1, t2-t when low level
5. The light is turned on, and the light turns off and on periodically while the key switch is pressed (as is clear from FIG. 4, the light-on time is longer than the light-off time per cycle).

On the other hand, the key input terminal connected to one of the key output terminals by the key switch is periodically brought to a high level, and the key-in encoder 21 is controlled to output a corresponding coded signal.
The instruction decoder 22 stores and holds the code signal and sends the contents of the code signal to the modulation circuit 27. The modulation circuit 27 pulse-modulates the carrier (45.5 KHz) supplied via the timing signal generation circuit 23 with the code signal. The pulse-modulated signal is applied to the base of the driving transistor 3 through the buffer circuit 28 and the output terminal O, and drives infrared light emitting diodes 4 and 5 connected between its collector and the battery 8 in accordance with the modulated signal.

The scan signal generation circuit 24 generates a signal while the key switch is being pressed, so the content of the input signal from the key switch being pressed is input to the key-in encoder 21 for a certain period of time from t1 to t5, and is input to the instruction decoder 22. Replace the contents (of course, the same contents will be replaced, but if the first one is stored with incorrect contents due to noise etc., the method of repeatedly replacing it is preferable because it can eliminate this error).

FIG. 5 shows another embodiment of the present invention according to FIG. 3, in which a display light emitting diode 15 is connected to the key input terminal I1. Therefore, the circuit 29' for absorbing the current flowing through the light emitting diode 15 is provided on the key input terminal I1 side. In FIG. 5, the high level and low level forms of the key output terminals φ1 to φ5 are reversed from those in FIGS. 3 and 4, as shown in FIG. 6. Further, the key input terminals I1 to I8 are at a high level when none of the key switches is pressed and are not in operation, but only the key input terminal to which a signal from the key output terminals I1 to I8 is received by the operation of the key switch becomes a low level. Now, to explain the case where the key switch S11 is pressed and the key output terminal φ2 and the key input terminal I3 are connected, the key input terminal I
The state No. 3 becomes low level during times t2 to t3 and t6 to t7 as shown in FIG. 6 I3. This signal is sent from the key-in encoder 21 to the current absorption circuit 2.
9', and the circuit 29' performs t2-t3, t6-t
Since it is turned on during the period 7 and its input terminal is set to a low level, the display light emitting diode 15 lights up. In this way, the light emitting diode 15 lights up at time t2.
Terminal I when lit at ~t3, t6~t7
1 also goes to low level from t2 to t3 and from t6 to t7, and there is a risk of confusion between I1 and I3 regarding the information content, but to prevent this, input terminals I2 to I8 other than input terminal I1 are selected. In this case, it is necessary to prevent the signal from I1 from being taken in as information. The input control circuit 32 controls this operation. Thus, in the embodiment shown in FIG. 5, it is necessary to add an input control circuit 32 having the above-mentioned functions.

According to the present invention, by using the key input terminal or output terminal of the IC without increasing the number of terminal pins of IC1, the IC can be integrated with a minimum number of external parts.
1 operation display can be performed, and there is an effect that there is no drawback that would impair the stability of the oscillation circuit as in the conventional case.

[Brief explanation of the drawing]

FIG. 1 is a drawing showing a conventional circuit device. FIG. 2 is a drawing of a circuit device implementing the present invention,
FIG. 3 is a detailed diagram of a part thereof, and FIG. 4 is an explanatory waveform diagram. FIG. 5 is a detailed diagram of a main part of another embodiment of the present invention, and FIG. 6 is an explanatory waveform diagram thereof. l1-l8...first line group, L1-L4...second line group, 1...IC, 2...matrix key switch device, S1-S32...key switch,
3... Drive transistor, 4, 5... Infrared light emitting diode, 6... Mode changeover switch, 8...
...Battery, 9...Ceramic filter, 15...
Light emitting diodes for indicating IC operation, I1 to I8...
...Key input terminal, φ1 to φ4...Key output terminal,
21... Key-in encoder, 22... Instruction decoder, 23... Timing signal generation circuit, 24... Scan signal generation circuit, 25
... Oscillator circuit, 26 ... Frequency divider, 27 ... Modulation circuit, 28 ... Buffer circuit, 29, 29' ... Current absorption circuit, 32 ... Input control circuit.

Claims (1)

[Scope of claim for utility model registration] (1) An IC that generates oscillation voltage in an external circuit using a ceramic filter as a resonator and a capacitor.
In a circuit arrangement in which a key switch is disposed at each intersection of a first line group and a second line group externally connected to the line, and the key switch selectively connects the intersection points, at least one line of the first line group or on at least one track of the second track group.
A circuit device characterized by connecting a light emitting diode for displaying IC operation. (2) The circuit device according to claim 1, wherein the intersection of the first and second line groups is formed within a matrix key switch device.