JPS60128540A - Test method of microcomputer built in analog circuit - Google Patents

Abstract

PURPOSE:To test simply an analog circuit of a device to be measured by a CPU itself by using a storage device operating the said CPU of the device to be measured and a proper external circuit or the like. CONSTITUTION:An A/D converter test program is fetched in advance to a CPU 31 via a connecting line 8. When the CPU31 outputs a digital value to a D/A converter device 9 according to the program, the digital value is converted into an analog value at the D/A converter device 9 and the analog value is inputted to an A/D converter 32 so as to A/D-convert data and compares it with a digital value inputted to the D/A converter device 9 via the connection line 10. Through the comparison above, tie defect of the A/D converter is discriminated.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for testing a microcomputer, and particularly to a method for testing a microcomputer incorporating an analog circuit such as an analog/digital converter (hereinafter referred to as an A/D converter).

Generally, in order to test a device with a mixture of digital and analog circuits, such as a microcomputer with a built-in A/D converter, it is necessary to use expensive test equipment that can test both digital and analog circuits, or to test devices that are exclusively designed for testing analog circuits. Relatively inexpensive testing equipment etc. are used. The case where a microcomputer with a built-in A/D converter is tested will be described below. A test method using such a test device is shown in FIG. 1 is the tester, 2 is the connection wire,
3 is a device to be measured, and 4 is a connection line.

When an analog value and a test pattern for operating the A/D converter are sent from the tester 1 via the connection line 2, the analog value is converted to a digital value by the device under test 3, and then sent to the tester via the connection line 4. It was taken to 1,
The A/D converter of the device under test 3 is tested by determining whether the digital value is correct. This method requires an expensive test device and also requires time for processing by the test device itself, which has the disadvantage that the test time increases and the throughput of the test device decreases.

An object of the present invention is to provide a simple method for testing the device, which overcomes some of the above-mentioned drawbacks.

The feature of the present invention is that by using a storage device and a digital/analog converter (hereinafter referred to as D/A converter) device to operate the device under test, the device itself can determine whether the function of the A/D converter is normal or abnormal. There is a self-examination to judge.

The present invention will be described below with reference to the drawings. FIG. 2 shows one embodiment of the invention. 3 is a device under test; is the central processing unit (hereinafter abbreviated as CPU) 32 is A
/D converter, 5 is a reset signal connection line, 6 is a clock signal connection line, 7 is a storage device, 8 is a connection line, 9 is a D/A converter device, 10. 11 and 12 are connection lines, 13 is a control unit, It is. Device under test, 9
A/f) When a clock signal is applied from the control unit 13 to the microcomputer 3 with a built-in converter via the connection line 6, and a reset signal is applied via the connection line 5 to start the test, the CPU3. A stored in the storage device 7 in advance in order to operate
/D converter test program is connected to C via connection line 8.
P U 3. It is taken into the.

CPU 3. follows the program and connects the incoming line 1o
, outputs a digital value to the D/A converter device 9, the digital value is converted to an analog value in the D/A converter device, and the analog value is connected to connection #i! 11 to the A/D converter 32 in the device under test 3.

CPU 3. operates the A/D converter 3□, converts the analog value into a digital value, and compares and determines the digital value input to the D/A converter device 9 via the connection line 1o. That is, the A/D near y bar 1' 32 iz"iEnormally, the digital value found in the A/D converter 32 is within the range of the A/D converter 32. It should be equal to the digital value output for vice 9. By performing this north wall test, it is possible to determine whether the converter is good or bad.

After completing the test on the arbitrarily set analog value input in this way, the same test is repeated for the analog value input that needs to be tested, and the final result of pass/fail is sent to the control unit 13 via the connection line 12. -reading measurement object 3
It is determined whether the product is good or bad.

A/1) The case of a built-in converter has been described above, but according to the present invention, the focus is on the general-purpose control function of the device under test, and testing of a microcomputer with a built-in analog circuit is performed using the CPU of the device. By using a storage device that operates C1) and an appropriate external circuit, the analog circuit of the device can be easily tested by the C1) U of the device itself.

[Brief explanation of the drawing]

Fig. 1 is a circuit diagram of a conventional test method for a microcomputer in which digital circuits and analog circuits are mixed, such as a microcomputer with a built-in A/D converter, and Fig. 2 is a test circuit diagram showing an embodiment of the present invention. It is. 1...Test device (tester), 2. -4.8,1
0゜11.12... Connection leg, 3... Device under test, 31... Central processing unit ts
(CPU), 32... Analog/digital converter (A/D converter) 5... Reset signal connection line, 6... Clock signal connection line, 7... . . . Memory device, 9 . . . Digital/analog converter (D/A converter) device, 13 . . . Control unit.

Claims (1)

[Claims] A method for testing an analog circuit built into a microcomputer, comprising means for storing an analog circuit testing program for operating the microcomputer, and generation or processing of input/output analog signals of the analog circuit under control of the microcomputer. generating or processing the input/output analog signals in accordance with the analog circuit testing program to determine whether the analog circuit is good or not.
A method for testing a microcomputer with a built-in analog circuit, characterized in that defects are tested by the microcomputer itself.