JPH0671208B2 - 1-chip microcomputer - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Field of Industrial Application The present invention relates to a one-chip microcomputer used in a remote control transmitter or the like.

(B) Conventional Technology Conventionally, for example, in a remote control device using infrared rays, a transmitter drives an infrared light emitting diode at a specific carrier frequency according to an operation of a push button switch or the like, and transmits code data to be transmitted. In response, the output is intermittently generated to generate an infrared pulse signal train.

The carrier frequency is, for example, 40 kHz, 37.9 kHz, 3
Different carrier frequencies such as 6.7 kHz are adopted for each manufacturer or each set. In this way, the control circuit that handles a rectangular wave signal of a predetermined frequency is generally operated and signal-processed by a microcomputer, except for a dedicated IC such as an IC for a remote control transmitter, and a predetermined signal such as the carrier signal. The rectangular wave signal is created by dividing the system clock of the microcomputer by an integer. For example, when using a 40 kHz square wave signal, set the system clock to 480 kHz and set this to 1 /
Generated by dividing by 12, and when using a rectangular wave signal of 37.9 kHz, set the system clock to 455 kHz and divide by 1/12 to generate 36.7 kHz.
When using the square wave signal of
It is set to 0kHz and is generated by dividing this by 1/12.

(C) Problem to be Solved by the Invention For example, in the infrared remote control device described above, the one-chip microcomputer for the transmitter is adapted to be compatible with any of a plurality of carrier frequencies adopted by each set manufacturer. This is very important. This is necessary when the cost is reduced by mass-producing the same type of LSI, and when the same remote control transmitter is used to control a plurality of sets.

However, generally, in a device that creates a rectangular wave signal of a predetermined frequency by dividing the system clock signal, the frequency of the rectangular wave is determined only by the frequency of the system clock signal and the division ratio, and the frequencies are close to each other. It was not possible to generate different frequency signals. That is, at the time when the system clock that realizes one target frequency is determined, the frequency that can be realized in another is determined.
It was possible to generate only discrete frequencies.
That is, the ratio of the frequencies of the two rectangular wave signals that can be realized by a single system clock is n: n + 1 (n = 1,2,3, ...) Even if they are closest to each other.

For example, the clock frequency used for a general remote control transmitter is 400 to 500 kHz, and the carrier frequency is 30 to 40 kHz, so the clock frequency is 440 kHz as an example, and when this is divided into 1/11, 40 kHz, 1/1
Dividing the frequency by 2 gives 36.7kHz, but could not obtain carrier signals of other frequencies close to each other, such as 37.9kHz.

Therefore, in the past, for example, the system clock frequency was set to 2M.
A high frequency such as Hz or 4 MHz was generated, and an integer frequency division was performed based on this clock frequency to generate a carrier signal of a predetermined frequency.

However, if the system clock frequency is increased in this way, the current consumption also increases substantially in proportion to the frequency, which shortens the life of the battery, and when trying to secure the conventional life, a large-capacity battery is used. Is required, and the entire remote control transmitter becomes large. Furthermore, an expensive one-chip microcomputer that operates at a high clock frequency must be used, which causes a problem that the cost of the entire device becomes high.

An object of the present invention is to eliminate the above-mentioned conventional problems by generating a plurality of types of rectangular wave signals having frequencies close to each other without increasing the system clock frequency.
It is to provide a one-chip microcomputer.

(D) Means for Solving the Problem The one-chip microcomputer of the present invention oscillates or stops oscillation in accordance with the state of the oscillation control signal, generates rectangular wave signals of different frequencies in the oscillated state, and A plurality of oscillator circuits that output one rectangular wave signal as a system clock signal, a divider circuit that divides the input signal with a dividing ratio that corresponds to the dividing ratio setting signal, and a plurality of oscillators that respond to the selection signal. A rectangular wave signal selection circuit that selectively supplies a single output of the circuit to the frequency dividing circuit as the input signal, and outputs the selection signal to the rectangular wave signal selection circuit, and outputs the selection signal to the frequency dividing circuit. A latch circuit that outputs a frequency ratio setting signal and outputs the oscillation control signal to each oscillation circuit, and an oscillation that detects a signal input from the outside and outputs the system clock signal. A system clock signal start-up circuit that gives an oscillation control signal to the circuit to bring the oscillation circuit into an oscillating state, a ROM in which a program executed by the CPU is written in advance, and the contents of the ROM are read in synchronization with the system clock signal , The program previously written in the ROM is executed to set the generation data of the selection signal, the generation data of the division ratio setting signal, and the generation data of the oscillation control signal in the latch circuit, respectively. It is equipped with a CPU.

(E) Action In the one-chip microcomputer of the present invention,
The plurality of oscillating circuits oscillate or stop oscillating according to the state of the oscillation control signal, generate rectangular wave signals of different frequencies in the oscillating state, and output one of them as a system clock signal. The frequency divider circuit divides the input signal with a frequency division ratio according to the frequency division ratio setting signal, and the rectangular wave signal selection circuit outputs a single output of the plurality of oscillation circuits to the frequency division circuit according to the selection signal. Supply selectively. The latch circuit outputs the selection signal to the rectangular wave signal selection circuit, outputs the division ratio setting signal to the frequency division circuit, and further outputs the oscillation control signal to each oscillation circuit. . The system clock signal starting circuit detects a signal input from the outside, gives an oscillation control signal to an oscillation circuit that outputs the system clock signal, and brings the oscillation circuit into an oscillating state. A program executed by the CPU is previously written in the ROM, and the CPU reads the contents of the ROM in synchronization with the system clock signal and executes the program to generate the selection signal for the latch circuit. Data, data for generating the frequency division ratio setting signal, and data for generating the oscillation control signal are set respectively. Because of this operation, by changing the generation data of the selection signal or the generation data of the division ratio setting signal for the latch circuit, as compared with the case of generating a rectangular wave signal from a single frequency. , It becomes possible to easily obtain a plurality of types of rectangular wave signals having frequencies close to each other without increasing the oscillation frequency of the oscillation circuit, and only the oscillation circuit that generates the actually used rectangular wave signal is in the oscillating state. Since the oscillation circuit can be put into the oscillation stop state, wasteful power consumption can be effectively suppressed. Furthermore, the oscillation circuit that outputs the system clock signal automatically enters an oscillation state by the action of the system clock signal starting circuit when any signal is input from the outside, so that no signal is input from the outside until then. In this case, the system clock is not generated, and the entire one-chip microcomputer enters the sleep state, and its power consumption is suppressed to the limit. Therefore, the overall power consumption is reduced, and the device can be easily applied as it is to a device using a battery as a power source, such as an infrared remote control transmitter.

Further, since the system clock is supplied from a single oscillation circuit, it is possible to operate with a constant system clock regardless of frequency selection of the rectangular wave signal. Therefore, unlike the case of switching the frequency itself of the system clock signal, an abnormal clock signal (noise) does not occur at the time of switching.

(F) Embodiment FIG. 1 shows a block diagram of an infrared remote control transmitter which is an embodiment of the present invention.

In FIG. 1, reference numeral 20 is a one-chip microcomputer, and externally, ceramic oscillators 21, 22 and a key switch 2 are provided.
Driving circuit 24 for driving 3 and infrared light emitting diode 25
Etc. are connected. 1-chip microcomputer 20
The internal structure is as follows.

Capacitors C1 and C2 are capacitors for fixing the potential and R, respectively.
1 is a damping resistor, R2 is a feedback resistor, 1 is an inverting amplifier when one input terminal a is at "H" level
It is a NAND gate. These circuits and the ceramic oscillator 21 connected to the outside form a rectangular wave oscillation circuit. Similarly, capacitors C3, C4, resistors R3, R4, NAND gate 2
And the ceramic oscillator 22 constitutes another rectangular wave oscillation circuit. The oscillation frequencies of these two oscillation circuits are mainly determined by the resonance frequencies of the ceramic oscillators 21 and 22 connected to the outside, and here the ceramic oscillators 21 and 22 resonate at 455 kHz and 440 kHz, respectively. The flip-flop 6 is set by operating the key switch 23 as described later and reset by a signal from the internal control latch 10. The AND gates 3 and 4 and the inverter 7 are gate circuits that output either one of the outputs of the two oscillation circuits to the OR gate 5. This AND gate 3,4,
The inverter 7, the OR gate 5, and the internal control latch 10 correspond to the rectangular wave signal selection circuit according to the present invention. The frequency dividing circuit 8 is a circuit that divides the output signal of the OR gate 5 by a set frequency dividing ratio and outputs a rectangular wave signal of a predetermined frequency. The frequency dividing circuit 8 is composed of a frequency divider using a multistage flip-flop and a preset register. There is. The AND gate 9 interrupts the rectangular wave signal output from the frequency dividing circuit 8 by the signal c, and outputs it from the signal output terminal OUT. The CPU 11 executes a program previously written in the ROM 12 to perform various calculations, sets a frequency division ratio for the frequency dividing circuit 8 via the internal control latch 10, and outputs control signals b, c, r. Output. R
AM13 is used as a working area when reading a key or generating a pulse signal train. The I / O port 14 generates a key strobe signal to the key switch 23 and receives the return signal.

The overall operation of the infrared remote control transmitter shown in FIG. 1 is as follows.

First, in the standby state where the key switch is not operated, the flip-flop 6 is in the reset state, and the signal a is "L".
Therefore, the output of the NAND gate 1 is always at "H" level. Therefore, the oscillation circuit using the ceramic oscillator 21 stops the oscillation operation, and the system clock is not supplied. At this time, since the output signal b of the internal control latch 10 is held at the "L" level state, the oscillation circuit using the ceramic oscillator 22 may also stop the oscillation operation. Therefore, almost no current flows through the one-chip microcomputer 20 composed of the C-MOS circuit.

In this state, if any key of the key switch 23 is operated, the flip-flop 6 is directly set and the signal a
Becomes “H” level. As a result, the NAND gate 1 acts as an inverting amplifier, the oscillation circuit using the ceramic oscillator 21 performs an oscillating operation, and supplies a rectangular wave signal as a system clock. As a result, the CPU 11 starts executing the program previously written in the ROM 12 from a predetermined address. For example, first, a key strobe signal is generated to the key switch 23 via the I / O port 14, the operated key is specified by reading the return signal, and a process corresponding to the key is performed. For example, when driving the light emitting diode 25 at a carrier frequency of 37.9 kHz, the control signal b of the internal control latch 10 is set to "L" level and
The dividing ratio 1/12 is set in the dividing circuit 8. Further control signal c
Is output based on the transmission data. As a result, the rectangular wave signal of 455 kHz generated by the oscillation circuit using the ceramic oscillator 21 is divided by the AND gate 3 and the OR gate 5 into the frequency dividing circuit 8
Entered in. The frequency dividing circuit 8 divides the input signal by 1/12 and supplies a rectangular wave signal of 37.9 kHz to one input of the AND gate 9. For example, when driving a light emitting diode with a carrier frequency of 40 kHz, the internal control latch 10
The control signal b is set to the "H" level and the frequency dividing ratio is set to 1/11 in the frequency dividing circuit 8. As a result, the NAND gate 2 operates as an inverting amplifier, the oscillation circuit using the ceramic oscillator 22 generates a rectangular wave of 440 kHz, and this is supplied to the frequency dividing circuit 8 via the AND gate 4 and the OR gate 5. Further, in the same manner, when the light emitting diode is driven at a carrier frequency of 36.7 kHz, for example, the control signal b is set to the “H” level and the frequency dividing circuit 8 is set to the frequency dividing ratio 1/12.

When the key operation is continuously performed, the key reading and the key transmission are normally performed alternately, and the operation is repeated until the key operation is completed. Further, when the unauthorized key operation is recognized, the key reading is repeated without transmitting the key operation until the correct key operation is performed or the key operation is completed. In this manner, when the key is read and the data is not transmitted, the control signal b
Is set to the “L” level and only the oscillation circuit using the ceramic oscillator 21 is oscillated to suppress the current consumption of the entire circuit.

When a series of transmission is completed, the control signal r of the I / O port 10 is set to "H" level. As a result, the flip-flop 6 is reset, the oscillation circuit using the ceramic oscillator 21 also stops operating, and returns to the standby state.

In the abnormal example, two oscillator circuits are provided, but more oscillator circuits can be provided. An example of selectively using four oscillator circuits is shown in FIG. FIG. 2 shows the circuit of the main part, and 21, 31, 32 and 33 are ceramic oscillators having different oscillation frequencies. The output of the oscillation circuit using the ceramic oscillator 21 is used as a system clock as in the example shown in FIG. The decoder 42 decodes the output of the internal control latch 43 and sets any one of the signals S0 to S3 to "H" level. NAND
The gates 34, 35 and 36 operate as inverting amplifiers when the output signals S1, S2 and S3 of the decoder 42 are at "H" level. Therefore, the ceramic oscillator 31, 32, 33 and the NAND gate 3
The oscillator circuit composed of 4,35,36 and other capacitors and resistors is selectively operated by the signals S1, S2, S3 output from the decoder 42. AND gates 37, 38, 39 and 40 are
The signals S0, S1, S2, and S3 output from the decoder 42 selectively OR gates the outputs of the four oscillation circuits.
Output to 41. In this way, rectangular wave signals having different frequencies can be selectively input to the frequency dividing circuit 8.

(G) Effect of the Invention According to the present invention, it is possible to generate several types of rectangular waves at adjacent frequencies without particularly increasing the system clock frequency. Therefore, for example, by applying it to a controller of an infrared remote control transmitter, it is possible to adapt to signal formats with different carrier frequencies, and to configure a small-sized and inexpensive device with low current consumption. Moreover, since a plurality of sets of oscillation circuits themselves for generating the system clock signal are not provided, a special circuit for preventing the generation of an abnormal clock signal that occurs at the time of switching the system clock signal is not necessary.
It can be constructed with a simple circuit.

[Brief description of drawings]

FIG. 1 is a block diagram of an infrared remote control transmitter which is an embodiment of the present invention. FIG. 2 is a circuit diagram of a main part of an infrared remote control transmitter according to another embodiment.

Claims (1)

[Claims] 1. A plurality of devices that oscillate or stop oscillating according to the state of an oscillation control signal, generate rectangular wave signals of different frequencies in the oscillated state, and output one of the rectangular wave signals as a system clock signal. An oscillator circuit, a divider circuit that divides an input signal with a dividing ratio according to a dividing ratio setting signal, and a single output of the plurality of oscillator circuits according to a selection signal to the dividing circuit. A rectangular wave signal selection circuit that selectively supplies as an input signal, outputs the selection signal to the rectangular wave signal selection circuit, outputs the division ratio setting signal to the frequency dividing circuit, and outputs the frequency dividing ratio setting signal to each of the oscillation circuits. A latch circuit that outputs an oscillation control signal and a system that detects an externally input signal and supplies the oscillation control signal to the oscillation circuit that outputs the system clock signal to bring the oscillation circuit into an oscillation state. A clock signal starting circuit, a ROM in which a program to be executed by the CPU is written in advance, the contents of the ROM are read in synchronization with the system clock signal, the program written in the ROM is executed, and the selection signal And a CPU for setting the generation data of the division ratio setting signal and the generation data of the oscillation control signal in the latch circuit, respectively.