JPH03292539A - Fault test system for mpu mounted printed board - Google Patents

Abstract

PURPOSE:To test a printed board to be tested by outputting the addresses, data and control input signals to an address bus, a data bus, and a control input pin of the printed board from a started debug tool in a test state and then carrying out the test of the printed board. CONSTITUTION:In a restart state, the output (connection) of an address bus 21a, a data bus 21b, and other control input pins included in a debug tool 2 is suppressed to a printed board 1. A bus buffer 25 is provided with a function that can secure the output (connection) of the buses 21a and 21b and the control input pins in a normal working state. Then these buses and control input pins are separated between the tool 2 and the board 1. As a result, the hardware and firmware tests are attained at the side of the board 1 despite such faults as short circuits, disconnection, etc., occurred at the buses 21a and 21b and the control input pins.

Description

[Detailed Description of the Invention] [Table of Contents] Overview Industrial Application Fields Conventional Technology and Problems to be Solved by the Invention Means for Solving the Problems Action Examples Effects of the Invention [Summary] Microprocessor (MPU) Regarding the method of testing printed circuit board failures by connecting a debugging tool to the socket on which the microprocessor (MPU) is mounted on the printed circuit board, it is necessary to connect the address bus, data bus, and other control input pins on the printed circuit board side. The purpose of this test is to solve the problem of the debug tool itself not being able to start up and testing the printed circuit board under test due to "short" or "break" faults that exist in the debug tool. address bus, data bus.

A bus equipped with a mechanism that suppresses output of other control input pins to the printed board at the start of the test, and outputs the address bus, data bus, and other control input pins to the printed board during the test operation. A buffer is provided for the address bus and data bus in the debug tool at the start of the test.

The test program of the debug tool is started using the control input pin, and during normal testing, the started debug tool sends addresses to the address bus, data bus, and control input pins of the printed circuit board.

The circuit board is configured to output data and control input signals to test the printed circuit board.

[Industrial application field]

The present invention relates to a method for testing a printed board for faults by connecting a debugging tool to a mounting socket of a printed board on which a microprocessor (MPU) is mounted.

With recent advances in semiconductor technology, microprocessors (MPUs) with various functions have been developed, and printed circuit boards equipped with various types of microprocessors (MPUs) have come to be used in various electronic devices. .

There are various types of microprocessors (MPUs) such as 8 bits, 16 bits, and 32 bits, and commercially available debugging tools are usually used to investigate faults in printed circuit boards equipped with these microprocessors (MPUs).

In this case, remove the microprocessor (MPU) from the socket in which the microprocessor (MPU) is inserted on the printed circuit board under test, connect the commercially available debugging tool there, and The processor (MPU) is likened to a microprocessor (MPU) on the printed board side, and addresses, data, and
The printed board is tested by outputting control input signals, but if there is a problem with the address bus, data bus, or control input pin of the printed board such as a "short circuit" or "disconnection", the debug tool's test program itself There is a problem where the PCB cannot be started up, making it impossible to test the printed board.
What is needed is a printed board testing system equipped with an MPU that can first start up the test program of the debug tool and make it testable regardless of the fault state of the printed board.

[Prior art and problems to be solved by the invention] Fig. 2 is a diagram explaining a conventional MPU-equipped printed board testing method, in which (a) shows an outline of the operation of a microprocessor (MPU), and (b) ) and (C) show a test method for an MPU-mounted printed board using a commercially available debugging tool.

First, an overview of the operation of a microprocessor (hereinafter referred to as MPU) will be explained.

[Initial operation 1 (a) As shown in the figure, when the MPU detects a "reset" signal by power-on reset, etc., it initializes the inside of the MPU and turns the "reset" signal "off".
When detected, restart operation is started.

The restart operation, as shown in FIG. This address is then used as the address of the restart processing routine to read the restart processing routine and execute each step.

To explain a specific example using an 8-bit MPU (address bus 16 bits, data bus 8 bits), ■ Reset Nakauchi initialization wait for reset off ■ Output restart address X'FFFE' → 'FF
Read the contents of the control memory (ROM) 22 at address FE.

■ Output risk address X'FFFF"=>'
Reads the contents of the control memory (ROM) 22 at address FFFF.

Suppose that the address 'FFFE' is 'AO' and 'FFFF'
If the address is °00゛, ■ As the program start address, use X'AOO
Outputs O'.

(2) Thereafter, the read data is executed as an instruction.

At this time, if the printed circuit board 1 on which the MPU is mounted has the following failure, the restart will fail and the subsequent processing routine will not be performed normally.

“Initial Failure Case” The following events are considered as hardware failures during the restart operation of the MPU 20.

(1) “Short” or “disconnection” of reset signal
If the internal initialization fails, the liver U2
0 cannot output the restart address ('AOOO'), resulting in "no response" and "runaway" phenomena.

For example, if the reset signal is short-circuited to ground (GND), the reset state is excellent.

(2) If there is a "short circuit" or "disconnection" in the address bus lla of the printed board 1, the MPU starts processing by setting the contents of the data bus llb for the restart address as the "program start address". As a result, normal data, that is, the risk address X'AOOO' cannot be read, resulting in a "runaway".
It becomes a phenomenon.

For example, as mentioned above (D X'FFFE'=4X'FXFE'
T: If there is, "AO" cannot be read.

(3) Even if the address bus lla is normal, there is a "short circuit" in the data bus llb of the printed board 1.

Or, if there is a "break", the same phenomenon as (2) will occur, and normal data, that is, risk address X'AOOO'
cannot be loaded, resulting in a "runaway" phenomenon.

For example, even if the above-mentioned start address is X "FFFE", X'XO' is read instead of X'AO' as the data at that address.

(4) MPIJ address bus ll of printed board 1
a “Short” to control input pins other than data bus llb, such as volt (HALT) bins, interrupt pins, etc.

Or, if there is a "disconnect", depending on the content, the MPU will
This causes phenomena such as "out of control" and "no action".

In this way, a failure during the restart operation of the MPU 20 of the debug tool 2 appears as a phenomenon such as "runaway" or "no operation," and at this time, the MPU 20 cannot perform any operation, and the failure occurs. Investigations include visual inspection of the exterior, etc.
The current situation is that there is no fixed J in the research method, and the reality is that it has turned to ``track record'' and ``kan'' by experienced people.

[Failure 1 After Completion of Restart Processing After the MPU 20 of the debug tool 2 is restarted, the operation follows the contents of the firmware stored in the control memory (ROM) 22.

Possible failures while this firmware is being executed include: (1) failure of the temporary memory (RAM) 13 of the printed board 1, such as read/write failure, data conversion, etc.

2) Failure of the control memory (ROM) 12 of the printed board 1, for example, data conversion during reading.

3) Other registers (REG) on printed board 1 14.
Failures in highly integrated circuits (LSI), such as read/write malfunctions, data conversion, etc.

There is. However, these failures occur after the failure handling routine of the debug tool 2 is restarted, and it is necessary to check the normality of the restart process and recognize the failed address (for example, the failure address at address X'AAAA'). The data is,
By recognizing that the firmware list is different from the firmware list, etc., it is possible to relatively easily find a fault in one printed board using a debugging tool, which will be described later.

[Function 1 of commercially available debug cooler MPU mounted on printed board 1 (usually MP[
+ indicates socket mounting) from the socket, and instead connect the connector ■ on the debug tool 2 side to the soget of the MPU 10 on the printed board 1, as shown in the figure (b), and connect the connector inside the debug tool 2. The printed board 1 is tested using the MPU 20 of the following.

Therefore, in the case of a printed circuit board having the fault described in the section of "Initial Failure Case" above, it cannot function as a debugging tool due to a failure in the restart operation.

In other words, it is not suitable for fault investigation in the case of a printed circuit board 1 that has a hardware fault. In other words, these debugging tools 2 are debugging tools for developing firmware, and there is a precondition that the hardware is "normal".

That is, in the current debugging tool 2, as shown in FIG.

Since the debug bus and other control input bins 21 are directly connected to those on the printed board 1, "short" or "disconnection" may occur.
The state of the printed board 1 side, etc., is transmitted to the address bus, data bus, and other control input bins 21 in the debug tool 2.

The control input bin 21 becomes obstructed, and the test program itself of the debugging tool 2 cannot start normally, and therefore, the switches on the operation panel and the keys from the keyboard (KB) etc. are also disabled, and the debugging tool 2 had the problem that it could no longer function at all.

In view of the above-mentioned conventional drawbacks, the present invention provides a microprocessor (
When connecting a debug tool to the socket on which a microprocessor (MPU) is mounted on a printed circuit board to test for faults on the printed circuit board, the address bus, data bus, and other The purpose of the present invention is to provide a debugging tool that can solve the problem of the debugging tool itself not being able to start up and testing the printed circuit board due to a "short" or "disconnection" fault that exists in the control input bin. That is.

[Means to solve the problem]

The above-mentioned problems are solved by the test method of MPU-equipped printer) 1 configured as follows.

This method tests for faults by connecting a debugging tool to the socket on which a microprocessor (MP[I) is mounted, on a printed circuit board on which the microprocessor (MP[I) is mounted, and which includes an 8-bit debug cool address bus, data bus.

A bus buffer with a mechanism to suppress output of other control input bins to the printed board at the start of the test and to output the address bus, data bus, and other control input bins to the printed board during test operation is installed. At the start of a test, the debug program's test program is launched using the address bus, data bus, and control input in the debug tool, and during normal testing, the PC board's address bus, data bus.

The circuit board is configured to output address, data, and control input signals to control input bins to test the printed board.

[Effect]

That is, according to the present invention, the address bus, data bus, and other control input bins in the debug tool are inhibited from being output (connected) to the printed board side during restart operation, and are not output to (connected to) the printed board side during normal operation. Output (connect) address bus, data bus, and other control input bins to the printed board side
Provide a bus buffer with a mechanism that allows
The address bus, data bus, and control input bin are separated into the debug tool side and the printed board side.

Specifically, the bus buffer opens and closes the output (connection) of the address bus, data bus, and control input bin to the printed circuit board depending on the contents of the address bus of the debug module. That is, when the contents of the address bus are within the address and data area of the test program of the debug tool, outputting (connecting) the address bus, data bus, and control input bin to the printed board side is inhibited, and When the contents of the address bus indicate the address area to be tested, the address bus and data bus.

Output (connect) the control input bin to the printed board side.

Therefore, when the debug tool is restarted, it is not affected by the states of the address bus and data bus on the printed board side, and can immediately start up.

Then, when the fault handling routine after startup executes each instruction and reaches the output address, the bus buffer outputs the address and data output by the debug tool to the printed circuit board, so the execution result at that time is By recognizing this, it is possible to easily search for faults within the printed board.

Therefore, even if there is a failure such as a "short circuit" or "disconnection" in the address bus, data bus, or control input pin on the printed board side,
Hardware on the printed board side.

This has the effect of making it possible to test firmware.

〔Example〕

Embodiments of the present invention will be described in detail below with reference to the drawings.

FIG. 1 is a diagram showing an embodiment of the present invention, in which (a) shows an example of the overall configuration, and (b) shows an example of the configuration of a bus buffer, in which the contents of the address bus 21a of the debug tool 2 are shown. indicates an area to be used in the test program of the debug tool 2, it suppresses output (connection) of the address bus 21a, data bus 21b, etc. to the printed circuit board 1, and prevents the address from going outside the debug area. At some point, the address bus 21a + data bus 21b etc. are connected to the printed board 1.
A bus buffer 25 output (connected) to the side is a necessary means for implementing the present invention. Note that the same reference numerals indicate the same objects throughout the figures.

Hereinafter, a failure test method for a printed circuit board equipped with an MPU according to the present invention will be explained with reference to FIG.

First, as mentioned above, in debug tool 2, M
The restart operation of PU 20 is completed normally.
This is an essential condition for subsequent test operations.

Focusing on the fact that the address area used by the MPU 20 normally includes a program area (debug area) necessary for starting a fault handling routine and an area for accessing the test object, the present invention provides the following: a) As shown in the figure, in the address bus 21a and data bus 21 of the debug tool 2, the address bus 21a and the data bus 21
b. Insert a bus buffer 25 that separates the control input pins during restart operation and during normal operation.

Specifically, as shown in figure (b), the address bus 21
When the decoder (DEC) detects that the value of a is the address used in the fault handling routine, it prevents the address bus 21a, data bus 21b, and control input bin from being output to the connector ■ side. do.

When the value of the address bus 21a is outside the debug area, that is, the test object is accessed, the decoder (DEC) has no detection output, so the address bus 21a, the data bus 2xb, and the control It operates to output the input bin to the connector ■ side.

Hereinafter, a test method when using the debug tool 2 of the present invention will be explained.

a. First, implement liver U 20 in debug tool 2,
Remove MPU 10 from printed board 1.

b. Connect the debug tool 2 to the socket of the removed MPU 10 on the printed circuit board 1 via the connector (2).

c. A control memory (ROM) 22 in which control firmware is stored is incorporated into the debug tool 2.

d. As the control firmware, for example, "stop", "address comparison stop", "store", "load", etc. are prepared.

e, M When the debug tool 2 is started from a specific address, the contents "A" of the address bus 21a and data bus 21b are transferred to the address bus 11a and data bus 11brB of the printed board 1 by the bus buffer 25 of the present invention.
Since it is disconnected from J, the restart operation ends normally and the state becomes ready for testing.

10 Next, the MPU 20 controls the control memory (ROM) 22
When the control firmware is executed, values outside the debug area are output to the address bus 21a and data bus 21b, and the pass bar 411
a, output to data bus llb.

For example, by outputting address X'AOOO' for printed board 1 and comparing and checking the value of data bus llb at that time with the firmware list, it is easy to know whether there is a failure in one printed board. be able to.

In this way, the present invention operates the main address bus and data bus on the debug tool side separately from the address bus and data bus of the printed board under test at the time of restart, thereby making it easier to operate the address bus and data bus on the printed board side. The feature is that the MPU of the debug tool can be restarted no matter what kind of failure exists in the address bus or data bus.

〔Effect of the invention〕

As explained above in detail, the MPU-equipped printed board failure testing method of the present invention is based on the microprocessor (MPU)
) of the printed board on which the microprocessor ( ) is mounted.
When a debug tool is connected to the socket mounted on the MPU to test for faults on the printed circuit board, the address bus, data bus, and other control input pins of the debug tool are output to the printed circuit board at the start of the test. During test operation, the address bus, data bus, and other control input bottles are output (connected) to the printed board.
At the start of the test, the debug tool program is started using the address bus, data bus, and control input pins in the debug tool, and during normal testing, the debug tool program is Since the debug tool outputs address and data control input signals to the address bus and data bus of the printed board to test the printed board, it is possible to test the printed board regardless of the fault status on the printed board under test. First, there is an advantage that the printed board can be tested with the debug tool in a testable state.

[Brief explanation of drawings]

FIG. 1 is a diagram showing an embodiment of the present invention. FIG. 2 is a diagram illustrating a conventional MPU-equipped printed board testing method. It is. 25 is a bus buffer. ■ is a connector. are shown respectively. In the drawings, 1 is a printed board or a printed board to be tested. 10 is a microprocessor (MPU). 11 is an address bus and a data bus (B). 11a is an address bus, and llb is a data bus. 12 is a control memory (ROM). 2 is a debugging tool. 20 is a microprocessor (MPU). 21 is an address bus and a data bus (A). 21a is an address bus, and 21b is a data bus. 22 is a control memory (ROM). (c)

Claims (1)

[Claims] The microprocessor (MPU) (10) of the printed board (1) on which the microprocessor (MPU) (10) is mounted;
This method tests for faults by connecting a debugging tool (2) to the mounting socket of the debugging tool (10), the debugging tool (2) having an address bus, a data bus,
The other control input terminals (21) are inhibited from being output to the printed board (1) at the start of the test, and the address bus, data bus, and other control input terminals (21) are printed during the test operation. A bus buffer (25) with a mechanism for outputting to the board (1) is provided, and at the start of the test, the address bus, data bus, and control input terminal (21) in the debug tool (2) are used to Start up the debug tool test program, and during normal testing, the debug tool (2
) to the printed board (1) address bus, data bus,
A fault testing method for a printed circuit board equipped with an MPU, characterized in that the printed circuit board (1) is tested by outputting address, data, and control input signals to a control input terminal (11).