JP2920561B2 - Test method for one-chip microcomputer - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial applications]

The present invention relates to a method for testing a one-chip microcomputer using an in-circuit tester.

[Prior art]

When multiple circuit ICs are mounted on one board, each circuit IC is individually judged to be good or defective, and when all circuit ICs are good, the whole board is judged to be good. , An in-circuit tester is used. For example, a general-purpose CPU, that is, a program ROM is separate,
When testing a CPU that can be used for various purposes by replacing the program ROM with this in-circuit tester, the tester gives the CPU an instruction code, data, an interrupt signal, etc. The quality of this CPU is determined by detecting the address signal, data, and control signal output from the CPU by a tester.

[Problems to be solved by the invention]

By the way, for example, air conditioners and washing machines,
A one-chip microcomputer used in a refrigerator or the like has a ROM in which a program for specific control of each electric device is built in one chip. However, when trying to test this kind of one-chip microcomputer with an in-circuit tester, the program ROM is in the chip and the execution procedure of the instruction cannot be controlled from the outside, so that it cannot be tested by the usual method as described above. . For this reason, it is possible to test by analyzing the assembler for each chip or to detect whether or not a predetermined output is obtained when an actual input signal, for example, a signal that "the power switch is turned on" is input. I try to test. However, analyzing an assembler is very cumbersome and not suitable for a simple test method. In addition, a method of testing by inputting an actual input signal to the chip cannot be tested without knowing the program contents of the built-in ROM. In view of the above points, the present invention is simple for anyone.
An object of the present invention is to provide a test method capable of testing a chip microcomputer.

[Means for Solving the Problems]

The present invention provides a CPU, an input port, an output port,
The input port, the output port, the RAM, and the R in a one-chip microcomputer including an AM and a ROM in which an in-circuit test program is previously written.
A method of testing each of the OMs by using an in-circuit tester, wherein one of a plurality of terminal pins of the one-chip microcomputer is used as a test pin, and the test pin is used by the in-circuit tester. By changing the state from one state to another,
The test of the test object in the one-chip microcomputer is started, and then, by inverting the state of the test pin, the input port, the output port,
The test program of the in-circuit tester and the in-circuit test program written in the ROM are synchronized so that the RAM and the ROM are sequentially changed and tested in a predetermined order. The input port, the output port, the RAM, and the ROM in the one-chip microcomputer, which are obtained by the in-circuit tester. RAM, R
It is characterized in that the quality of the OM is determined.

[Action]

A program for an in-circuit test is written in a built-in program ROM, and the test pins are controlled according to, for example, a test program of an in-circuit tester, and a program for an in-circuit test of the ROM built in the one chip is provided. Are synchronized, and each unit in the one-chip microcomputer is sequentially tested. The tester can determine the quality of each part by sequentially obtaining test results of each part from the one-chip microcomputer.

【Example】

Hereinafter, a test method according to the present invention will be described with reference to the drawings. The one-chip microcomputer 10 of this example includes a CPU 11, a program ROM 12, a work area RAM 13, an input port 14, and an output port 15, as shown in FIG. Program ROM 12, work area RAM 13, input port
The output port 14 and the output port 15 are connected to the CPU 11 via a data bus 16 and an address bus 17. The input port 14 is connected to input pins P00, P01,..., P07, and the output port 15 is connected to output pins P10 to P17. Of the input pins P00 to P07, P00 is used as a test pin and is normally set to “high (= high level)”. Also, the signal supplied to the reset pin RS is “high”.
This one-chip microcomputer 10 is
Reset. A control program for specific control performed by the one-chip microcomputer 10 is written in the program ROM 12, and a test program described later for performing an in-circuit test of the one-chip microcomputer 10 is provided. Is written. When a plurality of circuit ICs are mounted on one board, the in-circuit tester 20 determines whether each circuit IC is good or not, and if all the circuit ICs are good, determines that the whole board is good. This is used for a test method that ensures that The in-circuit tester 20 is connected to the one-chip microcomputer 10 as follows. That is, the drive terminals D00 to D07 of the in-circuit tester 20 are connected to the input pins P00 to P07, the sensor terminals S00 to S07 are connected to the output pins P10 to P17 of the output port 15, and the drive terminal D08 is connected to the reset terminal. Connected to RS. In this example, the drive terminal D00 supplies a test control signal to the input pin P00. Then, the input test data is supplied from the drive terminals D01 to D07 from the tester 20 to the input pins P01 to P07 of the CPU 10. Then, when the test pin P00 is set to, for example, “low (= low level)” by the test program of the ROM 12, the test starts. Thereafter, the state of the pin P00 is inverted to test one chip. Each part of the microcomputer 10 is sequentially switched. Next, with reference to the flow chart of FIG. 2 and the flow chart of FIG. 3, which is a continuation of FIG. First, a one-chip microcomputer from tester 20
A "high" signal is supplied to the ten reset pins RS, and a signal for setting the input pin P00 to "low" is given (step 201). The one-chip microcomputer 10 is thereby reset (step 100), determines the state of the test pin P00 at that time (step 101), and if "high", shifts to a normal control program. If it is "low", the test starts, and it waits for the test pin P00 to become "high" (step 102). After step 201, the tester 20 gives a “low” signal to the reset pin RS of the one-chip microcomputer 10 and thereafter holds this signal to release the reset of the one-chip microcomputer 10 (step 202). Next, for example, [1010101] is applied to the input pins P01 to P07 of the input port 14.
Is given (step 203). Then, the test pin P00 is set to “high” (step 204). In the one-chip microcomputer 10, step 102
When it is detected that the test pin P00 has become “high”, an operation for checking the input port 14 and the output port 15 is performed. That is, the input pins P01 to P07
The data input to the input port 14 via the port is output to the output port 15 as it is (step 103). At this time,
If necessary, the input data may be subjected to a calculation, for example, an inversion process, and then the data may be output to the output port 15. The one-chip microcomputer 10 has an output port 15
After the data is output to the CPU, it waits until the test pin P00 becomes "low" (step 104). On the other hand, after the tester 20 sets the pin P00 to “high” in step 204, the CPU 11 checks the input port 14 and the output port 15 in the one-chip microcomputer 10.
Is completed (step 205), and when output data is output to the output port 15, this is captured (step 206). Then, it is determined whether or not the fetched data is an expected value (step 207). That is, the data input to the input port 14
Is output, the expected value is equal to the input data. If the input data is inverted by the one-chip microcomputer 10, the expected value is the inverted data of the input data [0101010]. Whether the input port 14 and the output port 15 are good or not can be determined based on whether or not the data is an expected value. If the captured data is different from the expected value, an error message is output,
For example, after printing out (step 208), the process proceeds to step 209. If the fetched data is as expected, the process jumps to step 209 to set the test pin P00 to "low". In the one-chip microcomputer 10, step 104
Then, it is detected that the test pin P00 has become “low”, and the operation of checking the ROM 12 is performed (step 10).
Five). The check of the ROM 12 is performed by, for example, a checksum of control program data. That is, ROM12
Contains the control program data (binary data) of 2
The sum by value calculation is obtained in advance, and the sum is stored in the ROM 12. Then, in the step 105 of checking the ROM 12, the control program data 2 of the ROM 12 is checked.
The sum is obtained by a value calculation, and the sum is compared with a previously stored sum to check the ROM 12. Based on the result of the check of the ROM 12 in step 105, the quality of the ROM 12 is determined (step 106).
If K, set “0” to output port 15 (step 1
08) If it is not OK, "1" is set to the output port 15 (step 107). Then, it waits until the test pin P00 becomes “high” (step 109). On the other hand, the tester 20 sets the pin P00 to “low” in step 209 and then sets the RO in the one-chip microcomputer 10 to “low”.
The process waits until the processing by the CPU 11 for checking M12 is completed (step 210), and when output data is output to the output port 15, it is fetched (step 211). Then, it is determined whether or not the fetched data is an expected value, that is, “0” (step 211). If the captured data is not “0”, an error message is output, for example, after printing out (step 213),
Proceeding to step 214, if the fetched data is "0", the process jumps to step 214 and sets the test pin P00 to "high". In the one-chip microcomputer 10, step 109
Then, it is detected that the test pin P00 has become “high”, and the operation of checking the RAM 13 is performed (step 1).
Ten). The check operation of the RAM 13 can be performed, for example, by once writing the input data into the RAM 13, reading the input data, reading the write data, comparing the read data with the read data, and determining whether the two match. Based on the result of the check of the RAM 13 in step 110, the quality of the RAM 13 is determined (step 111).
If K, set “0” to output port 15 (step 1
13) If it is not OK, "1" is set to the output port 15 (step 112). Thus, the test program on the one-chip microcomputer 10 ends (step 11).
Four). On the other hand, the tester 20 sets the pin P00 to “high” in step 214, and then sets the RA
The process waits until the processing by the CPU 11 for checking M13 is completed (step 215), and when output data is output to the output port 15, it is fetched (step 216). Then, it is determined whether or not the fetched data is an expected value, that is, “0” (step 217). If the received data is not "0", an error message is output, for example, after printing out (step 218),
Proceeding to step 219, if the fetched data is "0", the process jumps to step 219 to cancel all input signals. Then, the program ends (step 22).
0). As described above, the in-circuit tester 20 allows the internal parts of the one-chip microcomputer 10 with built-in ROM, that is, the input port 14, the output port 15, the ROM 12, and the RAM.
13 can be tested sequentially and automatically. The method of checking the quality of each part of the one-chip microcomputer 10 is an example, and it goes without saying that various check methods can be adopted. In addition, the order of checking each unit of the one-chip microcomputer 10 is not limited to the above example, but may be arbitrary. Further, the test pin is not limited to the input pin P00, and it goes without saying that another input pin can be used. Instead of printing out the error message, a display may be prepared in the tester 20 and displayed on the display.

【The invention's effect】

As described above, according to the present invention, the in-circuit test program is stored in the built-in ROM of the one-chip microcomputer, and one of the terminal pins of the one-chip microcomputer is used as a test pin. By performing the in-circuit tester operation in synchronization with the in-circuit test program of the in-circuit tester, it is possible to sequentially perform the in-circuit test on each unit in the one-chip microcomputer. According to the present invention, in-circuit tests of various one-chip microcomputers can be easily performed irrespective of the program contents of the built-in ROM of the one-chip microcomputer.

[Brief description of the drawings]

FIG. 1 is a diagram showing an example of a system configuration for implementing the method of the present invention, and FIGS. 2 and 3 are flowcharts for explaining an embodiment of the method of the present invention. 10; 1-chip microcomputer 11; CPU 12; ROM 13; RAM 14; input port 15; output port 20; in-circuit tester P00; test pins

Claims (2)

(57) [Claims] 1. A CPU, an input port, an output port, and a RAM.
And a ROM in which a program for in-circuit test has been written in advance, the input port, the output port, the RAM, and the R
A method of testing each of the OMs by using an in-circuit tester, wherein one of a plurality of terminal pins of the one-chip microcomputer is used as a test pin, and the test pin is used by the in-circuit tester. The state of the test target in the one-chip microcomputer is started by changing the state of the one-chip microcomputer from the one state to the other state, and thereafter, the state of the test pin is inverted, whereby In the test program of the in-circuit tester, the input port, the output port, the RAM, and the ROM to be tested are sequentially changed in a predetermined order and tested. Execute the test in synchronization with the written in-circuit test program. The input port, the output port, the RAM, the RAM, and the test result of the input port, the output port, the RAM, and the ROM in the one-chip microcomputer obtained by the in-circuit tester. R
A test method for a one-chip microcomputer, wherein the quality of an OM is determined. 2. The in-circuit tester inputs predetermined input data to the input port, and outputs the input data.
Obtaining an output result from the CPU from the output port, and determining whether the input port and the output port are good or bad; and determining whether the ROM is good or bad based on a total result of a binary operation of the control program data in the ROM. And transmitting the result of the determination from the one-chip microcomputer to the in-circuit tester.Writing and reading of predetermined data to and from the RAM to determine the quality of the RAM, and The method for testing a one-chip microcomputer according to claim 1, further comprising: transmitting the signal from the one-chip microcomputer to the in-circuit tester.