JPH06309104A - Digital controller equipped with analog input/output function - Google Patents

Abstract

PURPOSE:To input/output a corrected analog signal without increasing burden on a CPU by automatically performing adjustment for the correction of a conversion error between an analog signal and a digital signal. CONSTITUTION:An input/output circuit 18 provided with memory 18a in which correction data is stored is provided between the CPU 11 and signal conversion means 13, 14, and the transfer of the digital signal is performed by reading out the correction data in the memory 18a when the analog signal is inputted/ outputted. A test device 4 which performs the transfer of the analog signal with the signal, conversion means 13, 14 and notifies the digital signal in accordance with the analog signal to the CPU 11 is provided, and the correction data is written on the memory 18a by finding by the CPU 11.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a digital controller having an analog input / output function.

[0002]

2. Description of the Related Art A digital control device for converting an analog signal such as voltage or current into a digital signal for processing and converting the digital signal into an analog signal for output is generally used in many fields. There is.

FIG. 6 shows an example of the main configuration of a conventional device of this type.
It shows in (a). In FIG. 6A, reference numeral 1 is a digital control device and 2 is a test device thereof. The digital controller 1 takes in digital data, processes it, and outputs digital data. CPU 11, data input / output circuit
12, A / D converter for converting analog signals to digital signals 13, D / for converting digital signals to analog signals
An A converter 14 and a serial transmission interface 17 for outputting a digital signal to the outside are provided. In the above configuration, the analog signal D _a1 input to the A / D converter 13 is converted into a digital signal and the CPU via the input / output circuit 12.
Taken in 11. The digital signal output from the CPU 11 is applied to the D / A converter 14 via the input / output circuit 12, converted into the analog signal D _a2 , and output. When mutual conversion is performed between an analog signal and a digital signal in this way, an error may occur due to variations in the circuit constants of the analog circuit. FIG. 6B shows the conversion error characteristic between the analog signal and the digital signal in an exaggerated manner. In contrast to the ideal conversion characteristic (A), the actual conversion characteristic is offset error as shown in (B). , And has a proportional gain error. In order to correct these errors, the A / D converter 13 is provided with connection terminals for the variable resistors 15 and 16, and the errors are minimized by adjusting the variable resistors 15 and 16. The same correction is performed on the D / A converter 14.

As another correction method, a nonvolatile memory 12a such as an E ² PROM is provided in the input / output circuit 12, and an offset required for correction calculation is provided corresponding to the A / D converter 13 and the D / A converter 14. Data of the error and the proportional gain error is written in, and each time data is input to or output from the A / D converter 13 or the D / A converter 14, the data of the corresponding converter is taken out from the nonvolatile memory 12a. There is a method of performing correction calculation.

[0005]

In the above-mentioned conventional correction method, there is a possibility that the set resistance value may change due to deterioration of the contact portion of the variable resistance to cause malfunction, and there is a concern that it may change over time, and the resistance value should be adjusted. It had to be done manually, and the process of testing and adjusting the electronic module could not be completely automated.

Further, in the method using the non-volatile memory,
There is a problem that the CPU needs to perform arithmetic processing for the correction, and the execution time of the CPU increases and the time available for the original control arithmetic decreases.

The present invention has been made to solve the above problems, and an object thereof is to use a memory storing data for correcting a conversion error between an analog signal and a digital signal. A digital controller equipped with an analog input / output function that adjusts and increases conversion error due to deterioration of a mechanical contact portion of a variable resistor, eliminates manual adjustment, and does not increase CPU execution time burden. To provide.

[0008]

To achieve the above object, the present invention provides a CPU for processing digital signals,
In a digital control device equipped with a signal conversion means for converting an analog signal into a digital signal for input / output, an input / output circuit having a memory storing correction data is provided between the CPU and the signal conversion means, and an analog signal is provided. At the time of inputting / outputting, the correction data of the memory is read and the digital signal is transmitted / received.

Further, a test device is provided for transmitting / receiving an analog signal to / from the signal converting means and for notifying the CPU of a digital signal corresponding to the analog signal.
The data is obtained by U and written in the memory.

Further, the input / output circuit is further provided with a circuit capable of reading / writing the memory from / to a personal computer, exchanges an analog signal with the signal converting means, and supports the analog signal. A test device for notifying the personal computer of the digital signal to be provided is provided, and the personal computer obtains the correction data and writes it in the memory.

[0011]

With the above structure, the memory of the input / output circuit stores the correction data for correcting the conversion error between the analog signal and the digital signal, and the memory can be used in the input / output cycle of the analog signal from the CPU side. It becomes possible to directly read the correction data of.

Further, the test apparatus enables the CPU to calculate the correction data for correcting the conversion error between the analog signal and the digital signal from the plurality of ideal values and the actually measured value and write the correction data in the memory.

Further, the calculation of the correction data and the writing into the memory can be performed by using a personal computer, which can be performed without increasing the load on the CPU.

[0014]

FIG. 1 shows an embodiment of the present invention. In FIG. 1, 3 is a digital control device according to the present invention, and 4 is a test device for adjusting this digital control device. CPU
11, the A / D converter 13, the D / A converter 14, and the serial transmission interface 17 are the same as the conventional ones, but the data input / output circuit 18 has an electrically writable read-only memory (E ² PROM) 18a, decoder 18b, and a special function according to the present invention.

First, the analog input (A / D conversion) will be described with reference to FIG. First, in order to measure the conversion error of the A / D converter 13, the reference voltage D _a1 is output from the test apparatus 4 and the measured value Din converted into a digital amount through the path shown by the thick line in FIG. Is read. In this case, the test apparatus 4 causes the CPU 11 to separately read the ideal value of the digital amount to be output by the A / D converter 13 by serial transmission, and stores the measured value and the ideal value as a pair. Test device 4 is A /
A plurality of reference voltages D _a1 having different values are sequentially output within the allowable input range of the analog input of the D converter 13, and a plurality of actually measured values and ideal values corresponding thereto are obtained. Next, the CPU 11 uses these data to calculate a digital value on the ideal value side corresponding to the digital value of the entire range viewed from the measured value side, and FIG.
The digital values on the ideal value side are written in the memory 18a while sequentially specifying the addresses corresponding to the digital values in the entire range viewed from the measured value side on the route indicated by the thick line.

An example of an ideal value and an actual measurement value when the reference voltage is set at two points of 10.00 V and 0.00 V is shown in FIG. 4A, and a graph obtained by linearly interpolating between the two points is shown in FIG. ). In the figure, the characteristic A is an ideal value, and the characteristic B is an actually measured value.
From FIG. 4 (b), y is the ideal value and x is the measured value.
Substituting each data into the functional formula of = ax + b

[0017]

## EQU1 ## The constants a and b are obtained from the simultaneous equations of 1000 = 990a + b (1) 0 = 10a + b (2),

[0018]

## EQU00002 ## y = 1000x / (990-10) -1000.times.10 / (990-10) (3) The relational expression between the ideal value y and the measured value x can be obtained. After obtaining the above relational expression, the CPU 11 writes the value of the ideal value y corresponding to the entire range (10 to 990) of the measured value x in the memory 18a by using the value of x as an address.

After the writing to the memory 18a is completed, the CPU 11 confirms whether or not the written data is correctly read by the path shown by the thick line in FIG. 2C, and the work for the test adjustment is completed.

The route shown by the thick line in FIG. 2D shows the route when the digital control device 3 takes in an analog signal in the actual operation. That is, when the CPU 11 reads the analog input in the operating state,
The conversion data (measured value) Din of the A / D converter 13 is stored in the memory 18
The data (ideal value) of the corresponding address used for addressing a and read out is fetched as an analog signal. As a result, even if there is a conversion error in the A / D converter 13, the CPU
For 11, the corrected ideal value can be input by analog input.

In the case of analog output, the data flow is opposite to that of the above analog input, but the correction method can be performed in the same manner. That is, the CPU 11 sequentially outputs a plurality of digital values (ideal value Dout) having different values within the allowable input range of the D / A converter 14 along the path indicated by the thick line in FIG. In step 4, it is converted again into a digital value (measured value) and sent to the CPU 11 by serial transmission.
The PU 11 stores a plurality of ideal values and measured values in pairs. Note that the A / D conversion in the test apparatus 4 is assumed to be an ideal conversion with no error.

The CPU 11 uses these data to calculate the correction data in the same manner as described above, writes the correction data in the memory 18a through the bold line route shown in FIG. 2B, and confirms and adjusts the test through the bold line route shown in FIG. 2C. finish. When outputting an analog signal in the actual operation state, the CPU 11 outputs a digital value through the bold line path in FIG. 3B, and the corrected digital value is output from the memory 18a by using the ideal digital value as an address. . This allows the CPU 11 to output an analog signal corresponding to the ideal value even if the D / A converter 14 has a conversion error.

As shown in the second embodiment of FIG. 5, the present invention can be configured so that the correction calculation and the writing of the correction data are performed by using the personal computer 5.
According to this configuration, the test adjustment work is performed by the personal computer 5, so that the CPU 11 only needs to perform the gate control of the input / output circuit 18 in the actual operating state, and the configuration can be simplified.

[0024]

According to the present invention, the correction data for correcting the conversion error between the analog signal and the digital signal can be automatically written in the memory, so that the manual adjustment becomes unnecessary and the test adjustment process is automated. can do.

Further, it is possible to provide a digital control device having an analog input / output function capable of reading the correction data of the memory in the input / output cycle of the analog signal without increasing the load on the CPU.

[Brief description of drawings]

FIG. 1 is a configuration diagram showing an embodiment of the present invention.

FIG. 2 is a diagram showing a signal flow for explaining the operation of the embodiment.

FIG. 3 is a diagram showing a signal flow for explaining the operation of the embodiment.

FIG. 4 is a diagram showing an example of an ideal value and an actually measured value in the above embodiment.

FIG. 5 is a configuration diagram showing a second embodiment of the present invention.

FIG. 6 is a configuration diagram of a conventional device and a signal conversion characteristic diagram.

[Explanation of symbols]

3 ... Digital control device 4 ... Test device 5 ... Personal computer 11 ... CPU 13 ... A / D converter 14 ... D / A converter 17 ... Serial transmission interface 18 ... Input / output circuit 18a ... Memory

Claims (3)

[Claims] 1. A CPU for processing digital signals,
In a digital control device equipped with a signal conversion means for converting an analog signal into a digital signal for input / output, an input / output circuit having a memory storing correction data is provided between the CPU and the signal conversion means, and an analog signal is provided. A digital control device having an analog input / output function, wherein the correction data in the memory is read and a digital signal is transmitted / received at the time of input / output. 2. A digital control device having an analog input / output function according to claim 1, wherein a test for transmitting / receiving an analog signal to / from the signal converting means and notifying a digital signal corresponding to the analog signal to the CPU. A digital control device having an analog input / output function, characterized in that a device is provided, and the correction data is obtained by the CPU and written in the memory. 3. A digital control device having an analog input / output function according to claim 1, wherein the input / output circuit is further provided with a circuit capable of reading and writing the memory with a personal computer. A test device for transmitting and receiving an analog signal to and from the signal converting means and notifying a digital signal corresponding to the analog signal to the personal computer, the personal computer determining the correction data and writing the correction data in the memory. A digital controller with analog input / output function.