JP2001111389A - Microcomputer incorporating cr oscillation clock - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a microcomputer incorporating a CR oscillation clock with further precise clock precision without any cost increase. SOLUTION: This microcomputer incorporating a CR oscillation clock is provided with a CR oscillation clock for automatically adjusting an oscillation cycle based on a precise outside oscillation pulse. This CR oscillation clock is provided with a CR oscillation circuit 1 having a ladder resistance 11, an edge detecting circuit 2 for detecting the edge of the oscillation output, an outside oscillation pulse counter 3, a count number setting register 4, a comparing and adjusting means 5 for comparing the numerical values of the counter 3 with those of the register 4, and for properly adjusting the ladder resistance 11, and a resistance adjusting circuit 6. In this CR oscillation clock, the oscillation cycle is automatically adjusted based on the precise outside oscillation pulse so that the clock precision of the CR oscillation clock can be accurately held. Also, the CR oscillation clock is formed as one part of an integrated circuit so that there is no cost increase.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention belongs to the technical field of microcomputers, and more particularly to the technical field of microcomputers having a built-in CR oscillation clock.

[0002]

2. Description of the Related Art Conventionally, microcomputers having a built-in inexpensive CR oscillation clock for the purpose of time control such as a sleep function and PWM control have been widely used. When such a microcomputer with a built-in CR oscillation clock is manufactured by an inexpensive ordinary process without adjustment man-hours, C
An error of several tens% occurs in the time accuracy of the R oscillation clock.

Therefore, as a conventional technique, a microcomputer with a built-in CR oscillation clock in which an error in the CR oscillation clock is suppressed to several percent by incorporating an adjustment resistor in the CR oscillation clock and performing laser trimming processing on the adjustment resistor. is there.

[0004]

However, in the prior art microcomputer with a built-in CR oscillation clock,
In performing laser trimming, a step of forming a thin film and a step of performing laser trimming are required, and there has been a disadvantage that the cost is increased by the number of steps. On the other hand, a microcomputer with a built-in CR oscillation clock manufactured by a normal process without laser trimming as described above has an error of several tens of percent. Too big. Therefore, a microcomputer having a CR oscillation clock which is inexpensive and has higher timekeeping accuracy, which is a conflicting demand in the past, is required.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a microcomputer having a built-in CR oscillation clock having more accurate timekeeping with little increase in cost.

[0006]

In order to solve the above problems, the inventors have invented the following means.

(First Means) A first means of the present invention is a microcomputer with a built-in CR oscillation clock according to the first aspect.

That is, the CR oscillation clock built in the microcomputer of this means has a CR oscillation circuit, an edge detection circuit, an external oscillation pulse counter, a count setting register, a comparison adjustment means, and a resistance adjustment circuit. Some of these components may be integrally formed with each other.

Here, the CR oscillation circuit is an oscillation circuit having a variable resistor whose resistance value is variable by a control signal from a resistance adjustment circuit described later, and the edge detection circuit is an edge of an oscillation output from the CR oscillation circuit. Is a detection circuit that generates a detection signal by detecting The external oscillation pulse counter is C
This is a digital counter that receives an external oscillation pulse whose cycle is more precise than the oscillation output from the R oscillation circuit and counts the external oscillation pulse. On the other hand, the count number setting register
This register stores an appropriate count number of an external oscillation pulse corresponding to one cycle of the oscillation output from the CR oscillation circuit. Further, when receiving the edge detection signal from the edge detection circuit, the comparing and adjusting means compares the count number of the external oscillation pulse by the external oscillation pulse counter with the count number stored in the count number setting register, and determines the difference between the two count numbers. Means for generating an adjustment signal for adjusting the oscillation cycle of the CR oscillation circuit based on the The resistance adjustment circuit is a circuit that generates a control signal based on an adjustment signal from the comparison adjustment unit and adjusts the resistance value of the variable resistor using the control signal.

Therefore, in this means, when one cycle of the CR oscillation circuit passes and the edge of the pulse of the oscillation output from the CR oscillation circuit is detected by the edge detection circuit, the detection signal is sent from the edge detection circuit to the comparison adjustment means. Sent. Then
The comparing and adjusting means reads out the integrated value of the external oscillation pulse integrated from the previous detection signal and the count number set in the count number setting register and compares them. Here, the count number set in the count number setting register is a proper integrated value of the external oscillation pulse which should correspond to one cycle of the oscillation output from the CR oscillation circuit. Therefore, the comparison and adjustment means uses an external oscillation pulse having a precise cycle
It is possible to determine how much one cycle of the oscillation output from the CR oscillation circuit is larger or smaller than an appropriate set value, based on how many times it is integrated in one cycle of the oscillation circuit. Based on the determination result, the comparing and adjusting means generates an adjustment signal for adjusting the oscillation cycle of the CR oscillation circuit, and based on the adjustment signal, the resistance adjustment circuit
A control signal is generated to adjust the resistance value of the variable resistor.

As a result, the oscillation cycle of the CR oscillation circuit is adjusted based on the external oscillation pulse with reference to the count number set in the count number setting register, so that the accuracy is equivalent to that of the external oscillation pulse having a precise oscillation cycle. It comes to have. Therefore, a microcomputer that incorporates a CR oscillation clock and performs time control based on the oscillation output from the CR oscillation clock can perform various time controls with fairly precise time accuracy. Since such a CR oscillation clock can be formed as a part of an integrated circuit of a microcomputer, the production of this means costs about 1 to 2 yen compared to a microcomputer having a normal CR oscillation clock. Only happens up.

Therefore, according to this means, a CR having a more precise timekeeping accuracy can be obtained with almost no increase in cost.
There is an effect that a microcomputer having a built-in oscillation clock can be provided. As a result, the microcomputer according to the present invention has an effect that various time controls can be performed with considerably precise time accuracy.

(Second Means) A second means of the present invention is a microcomputer with a built-in CR oscillation clock according to the second aspect. That is, the present means further includes count number limiting means for appropriately limiting the count number to be stored in the count number setting register. Here, the count number limiting means sets an appropriate range determined from an appropriate upper limit value and an appropriate lower limit value for the count number to be stored in the count number setting register, and sets the count value of the count number setting register to a value outside the appropriate range. If is specified, it has a function to forcibly set the count number to an appropriate default value.

In this means, even if an incorrect count number is written into the count number setting register due to some trouble or the like, the count number setting means operates the correct count number register. Is written. As a result, the control of the CR oscillation circuit is performed within an appropriate range, and the problem that the CR oscillation circuit becomes unable to oscillate or the oscillation cycle of the CR oscillation circuit becomes unstable is avoided.

Here, since the count limiting means can be formed as a part of the integrated circuit of the microcomputer, the present means can be implemented with almost no increase in cost.

Therefore, according to this means, in addition to the effect of the first means, there is an effect that a stable oscillating action of the CR oscillation circuit is guaranteed.

[0017]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of a microcomputer having a built-in CR oscillation clock according to the present invention will be clearly and fully described in the following embodiments so that those skilled in the art can understand the present invention.

Embodiment 1 (Configuration of Embodiment 1) A microcomputer with a built-in CR oscillation clock as Embodiment 1 of the present invention is a microcomputer with a built-in CR oscillation clock having the configuration shown in FIG. Here, this CR oscillation clock has a CR oscillation circuit 1, an edge detection circuit 2, an external oscillation pulse counter 3, a count setting register 4, a comparison adjustment means 5, and a resistance adjustment circuit 6.

The CR oscillation circuit 1 includes a resistance adjustment circuit 6 described later.
This is an oscillation circuit having a ladder resistor 11 as a variable resistor whose resistance value can be changed by a control signal from the control circuit. That is, C
The R oscillation circuit 1 is an oscillation circuit including a ladder resistor 11, a capacitor 12, an inverter (negative gate) 13, and a buffer 14. Here, the inverter 13 and the buffer 14 are respectively formed on the same chip as the microcomputer.

The edge detection circuit 2 is a detection circuit that detects an edge of the oscillation output from the CR oscillation circuit 1 and generates a detection signal.

The external oscillation pulse counter 3 has a CR
It is a digital counter that receives an external oscillation pulse from a crystal oscillator whose cycle is more precise than the oscillation output from the oscillation circuit 1 and counts the external oscillation pulse.

On the other hand, the count number setting register 4 stores the CR
This register stores an appropriate count number of an external oscillation pulse which should correspond to one cycle of the oscillation output from the oscillation circuit 1. That is, the count number set in the count number setting register 4 is set to a value by which the oscillation cycle of the CR oscillation circuit 1 should be adjusted during the time when the external oscillation pulse is generated by the count number.

Further, upon receiving the edge detection signal from the edge detection circuit 2, the comparison adjustment means 5 compares the count number of the external oscillation pulse by the external oscillation pulse counter 3 with the count number stored in the count number setting register 4. The digital operation means generates an adjustment signal for adjusting the oscillation cycle of the CR oscillation circuit 1 based on the difference between the two count numbers.

The resistance adjustment circuit 6 generates a control signal based on the adjustment signal from the comparison adjustment means 5, and adjusts the resistance value of the ladder resistor 11 as a variable resistor of the CR oscillation circuit 1 using the control signal. Circuit.

The above components 1 to 6 correspond to C of this embodiment.
It is integrated and formed integrally with a part of the integrated circuit of the microcomputer with the built-in R oscillation clock, and provides the microcomputer with a CR oscillation clock function.

The above-mentioned external oscillation pulse is provided from a crystal oscillation circuit whose oscillation cycle is precise, and the crystal oscillation circuit and the microcomputer with a built-in CR oscillation clock of this embodiment are provided with a sleep function to save power. Have

(Operation and Effect of First Embodiment) The microcomputer with a built-in CR oscillation clock of this embodiment has the above-described configuration, and thus exhibits the following operation and effect.

First, in a state where the above-described crystal oscillation circuit and the present one-chip microcomputer are functioning normally without being in the sleep state, the oscillation cycle of the CR oscillation circuit 1 is adjusted as follows.

That is, when one cycle of the CR oscillation circuit 1 has passed and the edge of the pulse of the oscillation output from the CR oscillation circuit is detected by the edge detection circuit 2, the detection signal is sent from the edge detection circuit 2 to the comparison / adjustment means 5. Sent. Then
The comparing and adjusting means 5 reads the count number of the external oscillation pulse integrated from the previous detection signal integrated by the external oscillation pulse counter 3 and the count number set in the count number setting register 4 and reads both. Compare. Here, the count number set in the count number setting register 4 is a proper integrated value of the external oscillation pulse which should correspond to one cycle of the oscillation output from the CR oscillation circuit 1. Therefore,
The comparison and adjustment means 5 determines which one cycle of the oscillation output from the CR oscillation circuit 1 is greater than the appropriate set value, based on how many external oscillation pulses having a precise cycle are accumulated in one cycle of the CR oscillation circuit 1. It can be determined whether the degree is large or small. Based on the determination result, the comparison and adjustment means 5 generates an adjustment signal for adjusting the oscillation cycle of the CR oscillation circuit 1, and based on the adjustment signal, the resistance adjustment circuit 6 generates a control signal. The resistance value of the ladder resistor 11 is adjusted.

The above operation will be described step by step with reference to the flowchart shown in FIG.

When the microcomputer with a built-in CR oscillation clock of this embodiment is started, the logic shown in the figure starts, and in a processing step S1, an appropriate initial value is substituted into the external oscillation pulse counter 3 for counting the initial oscillation. Is done. At the same time, in processing step S2, when an appropriate count number is registered in the count number setting register 4 and preparation for external oscillation pulse counting is completed, pulse oscillation from the CR oscillation circuit 1 starts in processing step S3. In the processing step S4, the rising edge of the pulse from the CR oscillation circuit 1 is detected by the edge detection circuit 2, and the judgment step S4 is performed.
At 5, the presence or absence of edge detection is determined. Then, the loop including the processing step S4 and the determination step S5 is repeated in a very short cycle until a rising edge is detected, and as soon as a rising edge is detected, the logic proceeds to the next determination step S6.

In the determination step S6, the count number indicating how many short-period external oscillation pulses have been counted until the rising edge of the pulse from the CR oscillation circuit 1 is detected is read out from the external oscillation pulse counter 3. The comparison between the count number registered in the count number setting register 4 and the magnitude is performed. If the integrated value of the external oscillation pulse counter 3 is smaller than the set value of the count number setting register 4, the logic proceeds to the processing step S
7, the resistance value of the ladder resistor 11 of the CR oscillation circuit 1 is increased by the operation of the comparison adjustment means 5 and the resistance adjustment circuit 6, and the transmission cycle of the CR oscillation circuit 1 is delayed. Conversely, if the integrated value of the external oscillation pulse counter 3 is larger than the value set in the count number setting register 4, the logic proceeds to the processing step S 8, and the operation of the comparison adjusting means 5 and the resistance adjusting circuit 6 causes the CR to operate. The resistance value of the ladder resistor 11 of the oscillation circuit 1 is reduced, and the transmission cycle of the CR oscillation circuit 1 is accelerated. In either case, that is, when the set value of the count number setting register 4 and the integrated value of the external oscillation pulse counter 3 are equal to each other, the ladder resistor 11 is not adjusted.

Then, in any case, the logic proceeds to the next processing step S9. In processing step S9, the count number accumulated by the external oscillation pulse counter 3 is cleared to zero, and the logic returns to processing step S4,
The loop of steps S4 to S9 is repeated.

As the loop is repeated, the integrated value of the external oscillation pulse counter 3 gradually approaches the set value of the count number setting register 4 and finally becomes almost the same or exactly the same. As a result, the oscillation cycle of the CR oscillation circuit 1 is adjusted based on the external oscillation pulse based on the count number set in the count number setting register 4, so that the accuracy according to the external oscillation pulse having a precise oscillation cycle is improved. I will have it.

Next, in this embodiment, since the CR oscillation circuit 1 is precisely adjusted in this manner, the above-described crystal oscillation circuit and the microcomputer of this embodiment save the CR oscillation circuit 1 to save power. Therefore, even in the sleep state, the sleep period is precisely controlled. As a result, the use purpose for which the setting of the precise sleep period is required is also reduced to C in this embodiment.
The microcomputer with the R oscillation clock can be used.

As described above, the microcomputer with a built-in CR oscillation clock of the present embodiment, that is, the microcomputer with a built-in CR oscillation clock and performing time control based on the oscillation output from the CR oscillation clock, has a very precise time accuracy. Various time controls can be performed. Then, even if the electrical characteristics of the ladder resistor 11 and the capacitor 12 of the CR oscillation circuit 1 are affected by the temperature change, the influence is immediately corrected, so that the oscillation cycle of the CR oscillation circuit 1 fluctuates due to the temperature change. Has also been prevented.

Note that such CR oscillation clocks (1 to
6) is formed as a part of the microcomputer integrated circuit as described above. Therefore, C of the present embodiment
To manufacture microcomputers with built-in R oscillation clock,
Compared with a microcomputer having a normal CR oscillation clock, the cost is only slightly increased by about 1 to 2 yen.

As described in detail above, according to the microcomputer with a built-in CR oscillation clock of the present embodiment, the cost accuracy is hardly increased, and the timing accuracy of the built-in CR oscillation clock can be improved without being affected by a temperature change or the like. There is an effect that precision can be achieved. As a result, the time control based on the built-in CR oscillation clock, such as the control of the sleep period, is assured fairly accurately. therefore,
The microcomputer with a built-in CR oscillation clock according to the present embodiment has an effect that it can be adapted to applications that require very precise CR oscillation clock time control.

(Modification 1 of Embodiment 1) As Modification 1 of the present embodiment, a CR that further includes count number limiting means (not shown) for appropriately limiting the count number to be stored in the count number setting register 4 is provided. A microcomputer with a built-in oscillation clock can be implemented. Here, the count number limiting means sets an appropriate range defined by an appropriate upper limit value and an appropriate lower limit value for the count number to be stored in the count number setting register 4, and sets the count of the count number setting register to a value outside the appropriate range. When a number is specified, it has a function to force the count to an appropriate default value.

In this modified embodiment, even if an improper count value is to be written into the count value setting register 4 due to some trouble or the like, the operation of the count value setting means 4 causes the count value setting register 4 to operate. Is written with a prescribed value in an allowable range. As a result, the control of the CR oscillation circuit 1 is performed within an appropriate range,
The disadvantage that the oscillation circuit 1 becomes unable to oscillate or the oscillation cycle of the CR oscillation circuit 1 becomes unstable is avoided.

Here, since the count number limiting means can also be formed as a part of the integrated circuit of the microcomputer, this modification can be implemented with almost no increase in cost.

Therefore, according to this modification, in addition to the effect of the first embodiment, even if the oscillation cycle of the CR oscillation circuit 1 can be changed, the stable oscillation operation of the CR oscillation circuit 1 is always guaranteed. effective.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating a configuration of a CR oscillation clock according to a first embodiment.

FIG. 2 is a flowchart illustrating an operation of a CR oscillation clock in the first embodiment.

[Explanation of symbols]

1: CR oscillation circuit 11: Ladder resistance (as a variable resistor) 12: Capacitor 13: Inverter (negative gate) 14: Buffer 2: Edge detection circuit 3: External oscillation pulse counter 4: Count number setting register 5: Comparison adjustment means
6: Resistance adjustment circuit

Continued on the front page (72) Inventor Keisuke Matsuda 1-1-1, Showa-cho, Kariya-shi, Aichi Prefecture Inside Denso Corporation (72) Inventor Hiroshi Fujii 1-1-1, Showa-cho, Kariya-shi, Aichi Prefecture F Inside Denso Corporation Term (reference) 5J043 AA22 EE01

Claims (2)

[Claims] 1. A microcomputer having a built-in CR oscillation clock and performing time control based on an oscillation output from the CR oscillation clock, wherein the CR oscillation clock is a variable resistor having a variable resistance value according to a control signal. A CR oscillation circuit having an edge detection circuit for detecting an edge of the oscillation output from the CR oscillation circuit; receiving an external oscillation pulse whose cycle is more precise than the oscillation output from the CR oscillation circuit; An external oscillation pulse counter for counting an oscillation pulse; a count number setting register for storing an appropriate count number of the external oscillation pulse corresponding to one cycle of the oscillation output from the CR oscillation circuit; When the edge detection signal is received from the external oscillation pulse counter, the external oscillation pulse count is stored in the count number setting register and the count number of the external oscillation pulse. It was compared with the count number, the C on the basis of the difference between the said count
Comparison adjustment means for generating an adjustment signal for adjusting the oscillation cycle of the R oscillation circuit; a resistance adjustment circuit for generating the control signal based on the adjustment signal and thereby adjusting the resistance value of the variable resistor; A microcomputer with a built-in CR oscillation clock. 2. An apparatus according to claim 1, wherein said count number to be stored in said count number setting register is provided with an appropriate range defined by an appropriate upper limit value and an appropriate lower limit value. 2. The microcomputer with a built-in CR oscillation clock according to claim 1, further comprising a count number limiter for forcibly setting the count number to an appropriate predetermined value.