JPS60160223A - Analog-digital converter - Google Patents

Abstract

PURPOSE:To attain execution of other job even during A/D conversion by using a hardware counter of a microcomputer to make the load of software and hardware of the microcomputer extremely light. CONSTITUTION:After a pulse count means 22 incorporated in the microcomuter 21 is cleared, a voltage generating means 20 is reset once at an output port 25. The A/D conversion is started at this point of time and an output pulse of a pulse generating means 19 is inputted to the pulse count means 22 and the voltage generating means 20. A voltage proportional to the pulse number is generated from the voltage generating means 20, and when the voltage is larger than an analog voltage 23 to be A/D-converted, the input of an output pulse of a pulse generating means 19 to the pulse count means 22 and the voltage generating means 20 is inhibited automatically and the A/D conversion is finished. That is, since the A/D conversion is finished automatically after the start by simply starting the A/D conversion, other job is performed for a time over the time required for the A/D conversion and when the job is finished, it is sufficient that the count value of the pulse count means 22 is inputted.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to an A/D conversion device that utilizes a hard counter built into a microcomputer (hereinafter referred to as a microcomputer).

Conventional configurations and their problems In recent years, the application of microcomputers to equipment has rapidly become widespread. Among these, the state input method is moving away from a simple digital input method to a method in which analog quantities are converted into digital quantities and input. There are two methods for this A/D conversion device, and the first method is to use an IC dedicated to A/D conversion, but this method is expensive and unsuitable for high-cost consumer equipment. Other methods include methods other than dedicated IC,
In other words, it is an A/D conversion device composed of multiple ICs and discrete parts, but it has a major drawback in that it cannot perform other tasks during A/D conversion, and if it is made to perform other tasks, This method has the disadvantage that the precision of the Le10 conversion deteriorates.

This conventional vlJ will be explained with reference to FIGS. 1 and 2.

In FIG. 1, 1 is a microcomputer, which has an output port 2 and an input port 3. The output port 2 receives a resistor A/D converted analog voltage (VA) 8, and the inverting input terminal 9 is connected to the ground via a capacitor 1o, and is connected to a DC power supply (V) 12 via a resistor 11. has been done. Further, the inverting input terminal 9 is connected to the collector of the transistor 6 via a resistor 13. The output of the voltage comparator 6 is an oven collector output, and is pulled up to a DC power supply (g) 12 by a resistor 14.

Next, the operation will be explained. FIG. g2 shows a part of a flowchart of A/D conversion under the control of the microcomputer 1 in the circuit configuration of FIG.

First, in step 14, the output port 2 is set to MI (4f), the transistor 6 is turned on, and the charge stored in the capacitor 1° is discharged via the resistor 13.

At this time, the output of the voltage comparator 6 is turned OFF because the voltage of the inverting input 9 is higher than that of the non-inverting input cuff, and the input port 3 is r
(It becomes IGH. In step 16, output port 2 is LOW.
Therefore, the transistor 5 is turned off, and the capacitor 1o changes from discharging to charging mode via the resistor 11.

Next, in step 17, it is checked whether input port 3 is LOW. Initially, since inverting input 9 is low, input port 3 is dIG
H, and the memory of the microcomputer 1 is counted up in step 18. That is, while the inverting input 9 is low, step 17
．． Continuing with the count amplifier, when the inverting input 9 becomes higher than the non-inverting input cuff, the output of the voltage comparator 6 becomes O.
becomes N, the input port 3 becomes LOW, A/D conversion ends, and the current value becomes the A/D converted value. There are differences depending on the microcomputer, but steps 17 and 18 alone take several 1oμSeC.
The above time is required, and the resolution of A/D conversion is poor.

Furthermore, if another job, ie, a step, is inserted between steps 17 and 18, the time will become even longer and the resolution will become extremely poor.

As mentioned above, the conventional method has the major drawback that other work cannot be done during A/D conversion, and conversely, when other work is performed, the resolution of A/D conversion becomes extremely poor. Ta.

Purpose of the Invention The present invention solves these conventional problems by using a microcomputer's hard counter, which is inexpensive, reduces the burden on the software and hardware of the microcomputer, and eliminates the need for other work even during A/D conversion. The object of the present invention is to provide an A/D conversion device that is capable of performing the following functions and has no effect on resolution.

Structure of the Invention The A/D converter of the present invention includes a pulse generating means for generating pulses, a voltage generating means for generating a voltage in proportion to the number of pulses, and an output voltage of the voltage generating means and an A/D converter. It has a voltage comparison means for comparing the magnitude of the converted analog voltage, and a pulse counting means built in a microcomputer, and the output of the pulse generation means is connected to each input section of the voltage generation means and the pulse generation means. , and said subject A/
When the output voltage of the voltage generating means becomes higher than the D-converted analog voltage, the output of the voltage comparing means is connected to inhibit input to the voltage generating means and the pulse counting means, and the output of the microcomputer is connected to reset the output of the voltage generating means.

DESCRIPTION OF THE EMBODIMENT FIG. 3 is a block diagram showing the configuration of an embodiment of the present invention.

Reference numeral 19 denotes a pulse generating means, and the output pulses of the pulse generating means 19 are connected to each input section of a voltage generating means 20 that generates a voltage in proportion to the number of pulses, and a pulse counting means 22 built in a microcomputer 21. ing.

23 is an analog voltage to be A/D converted, and voltage comparison means 24 compares the output voltage of the voltage generating means 20 with the analog voltage to be A/D converted.
/D conversion analog voltage 23 is compared and the voltage generating means 2
When the output voltage of 0 becomes larger than the A/D converted voltage 23, the voltage comparison means prevents the output pulse of the pulse generation means 19 from being input to the voltage generation means 2° and the pulse counting means 22. 24 outputs are connected.

Further, the output voltage of the voltage generating means 20 is reset by the output port 25 of the microcomputer 21.

Next, the operation of this embodiment will be explained. FIG. 4 shows the main part of the flowchart under control of the My/Carp 21.

In step 26, the microcomputer 21 clears the pulse counting means 22 built into the microcomputer 21. In step 27, the voltage generating means 20 is temporarily cooled at the output port 25 of the microcomputer 21. At this point, A/D conversion starts. That is, the output pulse of the pulse generating means 19 is input to the pulse counting means 22 and also to the voltage generating means 20. A voltage that is proportional to the number of pulses is generated from the output of the voltage generating means 20, and the output pulses of the pulse generating means 19 are input to the pulse counting means 22 and counted until the voltage becomes higher than the analog voltage to be A/D converted 23. Voltage generating means 2
o is input. The output of the voltage generating means 2o is
When the D-converted analog voltage becomes thicker, the voltage comparison means 24 automatically prohibits the input of the output pulse of the pulse generation means 19 to the pulse counting means 22 and the voltage generation means 20, and the A/D conversion ends. do.

Next, in step 28, another task is performed, and after a certain period of time has elapsed, in step 29, data from the pulse counting means 22 is inputted to obtain an A/D converted value.

In other words, by simply starting the A/D conversion in steps 26 and 27, the A/D conversion will automatically end after the A/D conversion starts, so you will not have to do other work that takes longer than the time required for the A/D conversion. If you leave it there, when the work is finished, the microcontroller 2
It is only necessary to input the count value of one pulse counting means 220, and the maximum resolution of A/D conversion is determined by the number of pits of the pulse counting means 22, and the accuracy does not change.

Next, a specific example of this embodiment is shown in FIG. 30 is a microcomputer with a built-in 4-bit serial counter 31.

32, 33, 34 are inverters and resistors 35, 36,
The capacitor 37 constitutes an oscillation circuit 38. At this time, the oscillation frequency F is obtained as F = (:M'z).

2.2C37R36 The output pulses of the oscillation circuit 38 are input to the serial counter 31 of the microcomputer 30 for counting via the resistor 39, and are also input to the binary counter 40, where the output pulses are 40 a , 40 b , 40 c' in proportion to the number of pulses. .

3CD code occurs on 40d.

This BCD code is input to a 4 btt ladder resistor 41, and a stepped voltage proportional to the number of pulses is generated from the output 41a. 42 is an analog voltage connected to the non-inverting input terminal 43a of the comparator 43. Further, the output 41a of the ladder resistor 41 is connected to the inverting input terminal 43b, and when the output voltage of the ladder resistor 41 becomes higher than the analog voltage 42, the comparator 43 is turned on, and the input of the pinary counter 40 and the serial counter 31 are turned on. The output port 44 of the microcomputer 30 is used to reset the pinary counter 40 by setting the input to LOilV to inhibit pulse input to the oscillation circuit 38. Figure 6 is the 5th
This is the manufacturing of each part in the figure. A is analog voltage 42, B
is the stepped output voltage of the ladder resistor 41. C indicates a pulse waveform input to the pinary counter 40 and serial counter 31.

That is, at point D, the comparator 43 is inverted, the pulse output of the oscillation circuit 38 is prohibited, and during this period the serial counter 31
The number of pulses input to becomes the A/D conversion value.

The maximum resolution of A/D conversion is the serial counter 31,
It is determined by counting, and since it is 4 bits in the embodiment, it is about 100 of the power supply voltage of the pinary counter 40. At this time, the maximum time T required for A/D conversion is obtained by the following equation.

T=1 eX"-=35.2CXR(sec)F 37
36. That is, it is necessary to have the user perform another task for a time longer than the maximum required time T, but if it is longer than that, there is no limit to the time and the burden on the software of the microcomputer 3o is extremely small. There is also a method of directly inputting the output of the binary counter 4o as the A/D conversion value, but the number of input ports of the microcontroller 30 increases and the hardware burden increases, but in the present invention, the serial counter 31 of the microcontroller 30 is used. Because of this, the number of microcomputer 3o boards is only two in total... - The burden on the board is small.

Effects of the Invention As is clear from the above actual gun example, the A/D conversion device of the present invention utilizes a hardware counter built into a microcomputer to detect the end of A/IT conversion by means of hardware (hardware), and converts it to a hard counter. In order to prohibit the pulse input of
A/D as microcomputer software
It is only necessary to start the conversion, and the A/D conversion value can be obtained by inputting the value of the internal hard counter when a certain period of time has elapsed. During that time, the software only needs to do other work for a certain amount of time, so the burden is small and the resolution is determined by the hardware, without the drawbacks of traditional methods. In addition, the number of microcomputer ports required for A/D conversion is low, the accuracy is high, and the burden on the microcomputer is low.
A D conversion device is obtained.

[Brief explanation of the drawing]

Figure 1 shows an A/C using a conventional microcomputer.
A circuit diagram of a D converter, FIG. 2 is a flowchart showing the main part of the microcomputer control of a conventional A/D converter, and FIG. 3 is a main part of an A/D converter showing an embodiment of the present invention. Fig. 4 is a flowchart showing the main part of the control of the microcomputer of the A/D converter;
FIG. 6 is a circuit diagram showing a specific example of the A/D conversion device.
The figure is a diagram showing signal waveforms at various parts in the same circuit. 19...pulse generating means, 2o...old voltage generating means, 21...mountain microcomputer, 22...
. . . Pulse counting means, 23 . . . Analog voltage to be A/D converted, 24 . . . Voltage comparison means. Name of agent: Patent attorney Toshio Nakao and 1 other person No. 5
Figure 6

Claims (1)

[Claims] A pulse generating means for generating pulses, a voltage generating means for generating a voltage in proportion to the number of pulses, and a voltage comparing means for comparing the output voltage of the voltage generating means with the analog voltage to be A/D converted. , has a pulse counting means built in the microcomputer, the output of the pulse generating means is connected to each input section of the voltage generating means and the pulse counting means, and the analog voltage to be A/D converted is Preferably, when the output voltage of the voltage generating means becomes large, the output of the voltage comparing means is connected to inhibit input to the voltage generating means and the pulse counting means, and the output of the microcomputer An A/D converter connected to reset the output of the voltage generating means.