JPS58214863A - Apparatus for detecting analogue voltage - Google Patents

Abstract

PURPOSE:To detect the arrival of an analogue input level inputted to a microcomputer to a predetermined level without delay, by indicating the output reversion of a comparator for comparing reference voltage and an input analogue signal. CONSTITUTION:A value set to a latch 1 corresponding to a program comes to reference voltage VR by a D/A converter 2 to be compared to the voltage V1 of an analogue signal inputted to a comparator 3 and the comparison output of the comparator 3 is reversed to either one of high and low outputs corresponding to whether the voltage V1 is equal to or higher than the voltage VR or not. This output and either one of high and low set values set to a latch are treated by an exclusive logical circuit 5 and FF 6 to indicate the reversion of the comparison output and the arrival of the inputted analogue input level to a predetermined level is detected without delay because of no sampling.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an analog voltage detection device, and in particular detects whether an analog signal input to a microcomputer equipped with an analog input terminal becomes equal to a preset voltage level. It is related to the device.

Most microcomputers equipped with a CPU, RAM, ROM, 1, 10, etc. receive digital signals as input, but circuits that can receive and process analog signals have also been developed. In a conventional microcomputer equipped with such an analog input, when detecting the voltage of an input analog signal, the A-D
Performs conversion (converting analog signals to digital signals). One method for A-D conversion is to provide dedicated hardware in advance and use the dedicated hardware to perform the A-D conversion.
- The conversion result is stored in a register with the number of bits depending on the resolution of the D converter. Another method has been proposed in which the input analog signal is compared with a preset voltage and the result is tested by a program.
A D conversion is performed. Regardless of whether the above-mentioned dedicated hardware or software is used, the conventional method only allows you to know the voltage level of the analog input signal at the time when an instruction related to A-D conversion is executed; It is not possible to know when a changing analog input signal has reached a certain voltage. In order to know when a changing analog input signal has reached a specific voltage, the main program must include multiple A-D conversion instructions and a processing routine to determine whether the result has reached a specific voltage. There is a problem in that it requires a lot of program area, and it takes more time than necessary to execute the main program. Also, since the A-D conversion command is executed at certain intervals during the execution of the main program, even if it is determined that the changing analog input has reached a certain voltage,
There is always a time difference in the sampling period, and the disadvantage is that the level of the analog input signal cannot be detected at a prompt timing.

Where analog input signal level detection is required,
It is not always the case that the voltage level itself of the input analog signal is required, but it is often the case that the signal is required to perform some processing when the voltage is equal to a certain voltage regardless of the progress of the potential change. be.

For example, when controlling temperature or humidity, there are cases where the temperature (humidity) is controlled to be within a certain range. This type of information, such as temperature or humidity, is usually input by converting it into an analog voltage using a sensor. Assuming that the temperature is currently lower than a predetermined temperature and heating is in progress, the control side only needs to give an instruction to stop heating as soon as the predetermined temperature is reached, and there is no particular requirement for any progress during the heating process.

The present invention does not require any processing until the input analog signal reaches a certain potential.In the analog voltage detection device, no consideration is required in the program until the difference between the specific voltage set in advance and the analog input signal becomes zero. A microcomputer that can immediately detect the state without any time delay when the difference between the two becomes zero, enter a processing routine to detect the level of the analog input signal, and output a detection signal. The present invention provides a simple signal level detection device.

FIG. 1 is a block diagram showing one embodiment of the present invention.
In a microcomputer equipped with J, a memory, an input section, an output section, etc., a first latch 1 consisting of n bits is provided, and a specific value serving as a reference is set in advance in the latch 1 by a program. The above latch l has n pins)D-A
A converter 2 is connected, and a reference voltage VR corresponding to a specific value of the digital signal stored in the ratte 1 is output as an analog signal. The reference voltage VR is applied to one input terminal e side of the comparator 3, and a comparison with the detected analog input signal V1 applied to the other input terminal θ side is performed in the comparator 3.

When the levels of the two human power signals are VR>Vl, the output of comparator 3 is "H" (high potential), and when VR<V, the output is "L" (low potential), and comparator 8 By detecting the time when the output changes from "H" to "L" or from "Ln" to "H", the time when the analog input signal ■□ matches the reference voltage ■8 can be detected. In the example, the analog input signal v
The level difference between the two human power signals became zero in the process where V1 changed from a level higher than the reference voltage vR to a lower level, or conversely, the level difference became zero in the process where V□ changed from a level lower than v8 to a level higher. This is an analog input signal detection device that can also detect whether the A second ratte 4 is provided to perform such a detection operation. The second latch 4 has a programmable structure similar to the first latch 1, and is previously set to "H" (high potential) or "L" (low potential) by the program. The "Hll" or "L" output of the second latch 4 is sent to the exclusive OR circuit 5 along with the output of the comparator 3.
and the exclusive OR of both human power signals is taken. When the second latch 4 is set to "H" by the program, when the output of the comparator 3 changes from "H'n" to "L", that is, the second As shown in straight line 2-1 in the figure, VR>v□
At time t1 when the voltage changes from vR to V□, the output of the exclusive OR circuit 5 changes from "L" to "H", and vice versa when the second latch 4 is set to "LIT". V (When changing from V to vR>vl (
At time 12) shown by the straight line 2-2 in FIG. 12, the output of the exclusive OR circuit 5 similarly changes from 'L' to 'H'.

Therefore, the analog input signal V1 is the preset reference voltage V
When the straight line 2-1 in FIG. 2 is closer to R than the low potential, the second latch 4 is set to "H++," and conversely, when the straight line 2-2 in FIG. Set the latch 4 of 2 to "LIT".

The output of the exclusive OR circuit 5 is given to the input of a flip-flop 6 which is set at the rising edge, and when the input changes from "L" to "H" as described above, an output signal Q is derived and the analog It is detected that the input signal V has reached the reference level vR set at the first level. The output signal Q of the flip-flop 6 is given as an interwoven control signal to various operation control circuits, for example, and commands control operations in accordance with the level of the detected analog input signal V□.

According to the above analog voltage detection device, the analog input signal V1 is changed to the reference voltage V by the output Q of the flip 70 knob 6.
In addition to knowing when the difference from R becomes zero, by testing the state of the second ratte 4 by the program, it is possible to determine whether V has changed from a value smaller than VR to equal to vR, or whether V□ is greater than vR. From a larger value, it can also be determined whether the value is equal to vR.

The comparator 3 in the above voltage detection device is VR>
The output is not limited to input/output related circuit configurations in which the output becomes "H" in the state of vl, but "H" in the state of vR=v1.
It can also be configured using a circuit that outputs 22 outputs.

In the circuit shown in FIG. 1 above, the first latte 1. Both the DA converter 2 and the comparator 3 are necessary for a microcomputer equipped with a normal analog input terminal, and are not specially added. This can be implemented by providing only a second latch 4, an exclusive OR circuit 5 and a clip-flop 6, and guiding the output of the seven lip-flops 6 to the interlaced control circuit.

The circuit for forming the interwoven control signal Q from the output of the comparator 3 is not limited to the above-mentioned embodiment, but is capable of detecting the change direction as well as the point of change in the output level of the comparator 3, and is implemented by a microcomputer. It can also be implemented by program processing.

As described above, according to the present invention, in a system that does not require processing until the input analog signal reaches a certain potential, it is possible to quickly detect the point in time when the analog input signal reaches a preset voltage level. No program consideration is required until the analog input signal becomes equal to vR, and the microcomputer can perform other controls without being bothered by voltage detection operations, making effective use of the microcomputer. can be achieved. Therefore, the program area of the microcomputer can be significantly reduced, which is particularly useful for one-chip microcomputers with limited program areas.

[Brief explanation of drawings]

FIG. 1 is a block diagram of main parts showing an embodiment according to the present invention,
FIG. 2 is a time change diagram of Vl for explaining the operation of the same embodiment. 1: first latch, 2: DA converter, 3: comparator, 4: second latch, 5: exclusive OR circuit, 6: 7 lip-flop.

Claims (1)

[Claims] l. A reference voltage generation circuit that outputs a preset voltage, a comparator that compares the output of the reference voltage generation circuit with an input analog signal, and an inversion of the comparator output. What is claimed is: 1. An analog voltage detection device comprising: a control signal generation circuit for detecting and forming a signal for instructing an inversion point, and detecting a point at which an analog input signal passes a predetermined level. 2. The control signal generation circuit includes a latch whose output state is set in advance, and an exclusive OR circuit in which the output of the latch is input to one side and the output of the comparator is applied to the other, exclusive and the input analog signal is higher than the reference voltage,