JPH0327624A - Rectangular wave signal generating circuit - Google Patents

Abstract

PURPOSE:To generate plural kinds of rectangular wave signals whose frequencies are close to each other, to attain low power consumption, miniaturization and low cost without special high system clock frequency by providing plural oscillation circuits, a frequency divider circuit and an oscillation signal selection circuit. CONSTITUTION:Two oscillation circuits comprising ceramic oscillators 21, 22 and capacitors C1-C4 or the like generate rectangular wave signals with different frequencies and at least one output is supplied as a system clock. Moreover, an oscillation signal selection circuit comprising AND gates 3, 4, an OR gate 5 and an internal control latch 10 or the like supplies a signal output from the two oscillation circuits to a frequency divider circuit 8 selectively, Then the circuit 8 divides the frequency of the output signal from the gate 5 with a preset frequency division ratio to output a rectangular wave signal with a prescribed frequency. Thus, plural rectangular wave signals with different frequencies are selected as input signals to the circuit 8 and the plural kinds of rectangular wave signals whose frequencies are close to each other are generated by the setting of the frequency division ratio so as to reduce the current consumption and the small sized and inexpensive device is constituted with a simple circuit.

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Field of Industrial Application This invention relates to a rectangular wave signal generating circuit used in remote control transmitters and the like.

(b) Prior Art Conventionally, for example, in a remote control device using infrared rays, a transmitter drives an infrared light emitting diode at a specific carrier frequency in response to the operation of a push button switch, etc., and also transmits code data to be transmitted. For example, the carrier frequency is configured to generate an infrared pulse signal train by intermittent output depending on the frequency.
Different carrier frequencies are adopted for each manufacturer or set, such as kHz, 37.9 kHz, and 36.7 kHz. In a control circuit that handles a rectangular wave signal of a predetermined frequency, calculations and signal processing are generally performed by a microcomputer, with the exception of a dedicated IC such as an IC for a remote control transmitter. The square wave signal is generated by dividing the microcomputer's system clock by an integer. For example, when using a 40kHz square wave signal, the system clock is set to 480kHz, and this is set to 1712kHz.
When using a 37.9kHz square wave signal generated by dividing the frequency, the system clock should be 4 5 5
If a 36.7 kHz square wave signal is used, the system clock is generated by dividing the frequency by 1/12.
Hz, and is generated by dividing the frequency by l/12.

(Problems to be solved by the Cl invention For example, in the above-mentioned infrared remote control device, it is necessary to make the one-chip microcomputer for the transmitter compatible with any of the plurality of carrier frequencies adopted by each cent manufacturer. This is important when reducing costs by mass producing LSIs of the same type, and when controlling multiple cents using the same remote control transmitter.

However, in a device that generates 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. However, it was not possible to generate different frequency signals at the same time. In other words, once a system frequency is determined to achieve one target frequency, other frequencies that can be achieved are determined, so only discrete frequencies can be generated. In other words, the ratio of the frequencies of two square wave signals that can be realized by a single system clock is n
:n+l (n=1, 23...).

For example, the crosslock frequency used in a -S remote control transmitter is 400 to 500 kHz, and the carrier frequency is 30 to 40 kHz. Dividing the frequency by 1/11 gives 40klIz, 1/1
If you divide the frequency by 2, you will get 36.7kHz, but for example, 37kHz.
．． It was not possible to obtain carrier signals of other nearby frequencies such as 9kHz.

Therefore, conventionally, for example, the frequency of the system clock was changed to 2.
A carrier signal of a predetermined frequency is generated by setting the frequency to a high frequency such as MHz or 4 MHz, and dividing the frequency by an integer based on this cross clock frequency.

However, if the system clock frequency is increased in this way, the current consumption will also increase approximately in proportion to the frequency, which will shorten the battery life. Batteries are required, and the entire remote control transmitter becomes larger. Furthermore, an expensive 1-chip microcomputer that operates at a high clock frequency must be used, which increases the cost of the entire device. An object of the present invention is to solve the above-mentioned conventional problems by generating multiple types of rectangular wave signals with close frequencies without particularly increasing the system clock frequency.
An object of the present invention is to provide a rectangular wave signal generation circuit.

(d) Means for Solving the Problems The rectangular wave signal generation circuit of the present invention includes a plurality of oscillation circuits each generating a rectangular wave signal of a different frequency by supplying any one output as a system clock; It is characterized by comprising a frequency dividing circuit that frequency divides a signal by a set ratio, and an oscillation signal selection circuit that selectively supplies a single output of the plurality of oscillation circuits to the frequency dividing circuit. .

(el effect) In the rectangular wave signal generation circuit of the present invention, the plurality of oscillation circuits generate rectangular wave signals of different frequencies,
At least one output is provided as a system clock. The frequency dividing circuit divides the frequency of the input signal by a set ratio, and the oscillation signal selection circuit selectively supplies the output of a single one of the plurality of oscillation circuits to the frequency dividing circuit.

Therefore, by selecting multiple rectangular wave signals with different frequencies as input signals to the frequency divider circuit and setting the frequency division ratio of the frequency divider circuit, generally used multiple types of rectangular wave signals with different frequencies that are close to each other can be generated. can be generated.

Furthermore, since the system clock is supplied from a single oscillation circuit, it can be operated with a constant system clock regardless of the frequency selection of the rectangular wave signal. For this reason, an abnormal cross signal (noise) is not generated at the time of switching, as in the case of switching the frequency itself of the system cross signal, for example.

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 denotes a one-chip microcomputer, to which a driving circuit 24 for driving a ceramic oscillator 2122, a key oscillator 23, an infrared light emitting diode 25, etc. are connected to the outside. The internal structure of the microcomputer 20 is as follows.

Capacitors Cl and C2 are potential fixing capacitors, R1 is a damping resistor, R2 is a feedback resistor, and 1 is a NAND gate that operates as an inverting amplifier 2Φ when one input terminal a is at the "H" level. A rectangular wave oscillation circuit is implemented by these circuits and a ceramic oscillator 21 connected to the outside. Similarly, capacitors C3 and C4, resistors R3 and R4, NAND gate 2 and ceramic oscillator 22 constitute another rectangular wave oscillation circuit.

The oscillation frequencies of these two oscillation circuits are mainly determined by the resonant frequencies of the externally connected ceramic oscillators 21 and 22, and here, the ceramic oscillators 21 and 22 have frequencies of 455 kHz and 440 kHz, respectively.
Resonates at Hz. The Frisop front panel 6 is set by operating the key switch 23 as will be described later, and reset by a signal from the internal control switch 10.

AND gates 3 and 4 and inverter 7 are gate 1 circuits that output one of the outputs of the two oscillation circuits to OR gate 5. These AND gates 3, 4, inharter 7, OR gate 5 and internal control launch 10
corresponds to the oscillation signal selection circuit according to the present invention. The frequency divider circuit 8 is a circuit that divides the output signal of the OR gate 5 by a set frequency division ratio and outputs a rectangular wave signal of a predetermined frequency. He is in charge. The AND gate 9 intermittents the intelligent wave signal output from the frequency dividing circuit 8 using the signal C, and outputs it from the signal output terminal OUT. The CPU II executes a program written in advance in the ROMI 2 to perform various calculations, and also sets the frequency division ratio for the frequency divider circuit 8 via the internal control processor 10, and also sends control signals b and c.
, r. The RAM 13 is used as a working area for key reading, pulse signal train generation, and the like. I/O port 14 generates a key strobe signal to key switch 23 and receives its return signal.

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

First, in the standby state where the key switch is not operated, the Frisopflosop 6 is in the reset state, and the signal a is "L".
”, and the output of the NAND gate 1 is always at the “H” level. Therefore, the oscillation circuit using the ceramic oscillator 2l has stopped its oscillation operation, and the system clock is not supplied. Also, at this time, the internal control Lunch 10
Since the output signal b is held at the "L" level, the oscillation circuit using the ceramic oscillator 22 also stops its oscillation operation. Therefore, almost no current consumption flows through the one-chip microcomputer 20, which is composed of a C-MOS circuit.

In this state, if any key of the key switch 23 is operated, the printer 6 is directly set and the signal a becomes "H" level. This allows NAND gate 1
acts as an inverting amplifier, and an oscillation circuit using a ceramic oscillator 21 performs an oscillation operation to supply a rectangular wave signal as a system clock. This causes the CPUII to RO
Execution of the program written in advance in M12 is started from a predetermined location. For example, first, a key 1 lobe signal is generated to the key isochi 23 via the I/O port 14, and the operated key is identified by reading the return signal, and processing corresponding to that 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 launch 10 is set to "L" level, and the frequency dividing circuit 8 is set to a frequency division ratio of 1/l2. Set. Furthermore, a control signal C is output based on the transmission data. As a result, the oscillation circuit using the ceramic oscillator 21 generates 455kHz.
The rectangular wave signal is input to the frequency dividing circuit 8 via the AND gate 3 and the OR gate 5. The frequency dividing circuit 8 divides the frequency of the input signal by 1/12 and provides a 379 kHz rectangular wave signal to one AND gate 9. Also, for example, 4
When driving the light emitting diode with a carrier frequency of 0 kHz, the internal control launch 100 control signal b is set to "H" level, and the frequency dividing circuit 8 is set to a frequency division ratio of 1/11. This allows NAND gate 2
operates as an inverting amplifier, and an oscillation circuit using a ceramic oscillator 22 generates a 440kHz rectangular wave, which is sent to a frequency dividing circuit 8 via an AND gate 4 and an OR gate 5.
supplied to Furthermore, in the same way, for example, 36.7kHz
When driving the light emitting diode at the carrier frequency, the control signal b is set to the "H" level, and the frequency dividing circuit 8 is set to a frequency division ratio of 1/12. When key operations are being performed continuously, the reading and sending of keys are normally performed alternately until the key operations are completed. Furthermore, when an unauthorized key operation is recognized, the data is not transmitted and the key reading is repeated until the correct key operation is performed or the key operation is completed. In this state where the key is read and not transmitted, the control signal b
By setting the voltage to "L" level and causing only the oscillation circuit using the ceramic oscillator 21 to oscillate, the current consumption of the entire circuit is suppressed.

When the series of transmissions is completed, the control signal r of the I/O boat 10 is set to the "!]' level. This resets the Frisopfurosop 6 and the oscillation circuit using the Cerami-Nok oscillator 2 also stops operating. and returns to standby mode.

In the example shown above, two oscillation circuits were provided, but more oscillation circuits may be provided. FIG. 2 shows an example in which four oscillation circuits are selectively used. Figure 2 shows the main part of the circuit, 21, 31, 32 and 3.
3 are ceramic oscillators having different oscillation frequencies. The output of the oscillation circuit using the ceramic cross oscillator 21 is used as a system cloth as in the example shown in Figure 1. The decoder 42 decodes the output of the internal control circuit 43 and outputs any one of the signals SO to S3 as "H".
” level, NAND gates 34, 35 and 36
In this case, the output signals S1, S2 and S3 of the decoder 42 are “H”.
'' level, each operates as an inverting amplifier. Therefore, the oscillation circuit consisting of the ceramic oscillators 31, 32, 33, NAND gates 34, 35, 36, and other capacitors and resistors receives the signal S output from the decoder 42.
It is selectively activated by L, S2, and S3. AND gates 37, 38, 39 and 40 selectively connect the outputs of the four oscillation circuits to OR gate 41 using signals So, 31, S2 and S3 output from decoder 42, respectively.
Output to. In this way, rectangular wave signals of different frequencies can be selectively input to the frequency dividing circuit 8.

(g) Effects of the Invention According to the present invention, several types of rectangular waves can be generated at adjacent frequencies without particularly increasing the system clock frequency. Therefore, by applying it to the controller 1 and roller of an infrared remote control transmitter, it can be made compatible with signal formats with different carrier frequencies.
Moreover, it will be possible to construct a small and inexpensive device with low current consumption. Moreover, since multiple sets of oscillation circuits that generate system clock signals are not provided, there is no need for a special circuit to prevent the generation of abnormal clock signals that occur when switching system clock signals, and a simple circuit is required. It can be constructed.

[Brief explanation of drawings]

FIG. 1 is a block diagram of an infrared remote control transmitter according to an embodiment of the present invention. FIG. 2 is a circuit diagram of the main parts of an infrared remote control transmitter {8m} according to another embodiment.

Claims (1)

[Claims] (1) A plurality of oscillation circuits that supply any one output as a system clock and generate rectangular wave signals of different frequencies, a frequency divider circuit that divides the input signal at a set ratio, and A rectangular wave signal generation circuit comprising: an oscillation signal selection circuit that selectively supplies a single output of the oscillation circuit to the frequency dividing circuit.