JPH04262426A - Microprocessor - Google Patents

Abstract

PURPOSE:To make debugging of the hardware of a microprocessor and its program by knowing the occurrence of runaway of the program and an address at which the runaway started. CONSTITUTION:In the initial state, the maximum value of the memory in the system is written in an upper boundary register 3, while in an lower boundary register 4 the minimum value of the memory in the system is written, and a compare circuit 6 is set up so as not to execute comparison with a value in a program counter 5. When starting the execution of the program, it is set so as to first write in the upper boundary register 3 the upper limit of a range that the program itself acts in the beginning and the lower limit thereof in the lower boundary register 4, followed by starting to make the compare circuit 6 carry out the comparison function. After that, the compare circuit 6 always compare the content in the program counter 5 with the contents of upper boundary and lower boundary registers 3 and 4, and when the value in the program counter 5 exceeds a range that boundary registers show, the compare circuit 6 externally informs of the situation through terminal 8 and at the same time a sequencer 7 is informed of this situation, and then stops the function of the compare circuit 6. Sequencer 7, when it is informed that the value in the program counter 5 exceeds the range, sets a predetermined specific value in the program counter 5.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a microprocessor incorporating a circuit for facilitating debugging during program development in a system using a microprocessor.

0002

[Background Art] When debugging a system under development in an information processing device, the flow of the program is executed one step or several steps at a time to check whether the hardware and software are working according to the intended logic. Conduct research.

[0003] In this case, once the hardware has started operating stably, defects can be discovered by following the logic of the software, but in the early stages of development when the hardware is not stable. The software may not work as intended, and the program may be executed in a memory area outside the program's operating range midway through execution. This is called a runaway program.

It is difficult to investigate the cause of this program runaway, and conventionally the cause has been traced by taking the operating waveforms of each part of the circuit and checking whether there are any abnormal operating waveforms. was going on.

[0005]

[Problems to be Solved by the Invention] With the conventional method described above, abnormal waveforms can only be captured by chance. Unable to investigate the inside of the vehicle, it was extremely difficult to determine the cause of the rampage.

[0006]

[Means for Solving the Problems] A microprocessor of the present invention includes a first boundary register indicating an upper limit of a program execution range, a second boundary register indicating a lower limit, and the first and second boundary registers. and a comparison circuit that compares the contents of the program counter with the value of the program counter having the program execution address, and when the program deviates from the range indicated by the first and second boundary registers during the execution of the program, the state is transmitted to the outside. The program is characterized in that it outputs a signal indicating the program, stops execution of the program, and passes control to a special program set in advance.

[0007] Furthermore, the program counter includes a register for saving the contents of the program counter immediately before the deviation from the range indicated by the first and second boundary registers.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, the present invention will be explained with reference to the drawings.

FIG. 1 shows a first diagram of a microprocessor according to the present invention.
It is a block diagram showing an example of. In the figure, the microprocessor includes a register file 1 consisting of a plurality of registers used for executing operations within the microprocessor, an arithmetic circuit 2 for executing operations, and an upper limit boundary register 3 having the upper limit value of the program. A lower limit boundary register 4 having the lower limit value of the program, a program counter 5, a comparison circuit 6 that compares the value of the program counter 5 with the values of the upper and lower limit boundary registers 3 and 4, and a sequencer 7 that controls the program execution order. , a terminal 8 for informing the outside that the program has crossed the boundary, and a local data bus 11 for transmitting data within the microprocessor.
It is equipped with

Next, a method for debugging using the microprocessor of this embodiment will be explained. In the initial state, the maximum memory value in the system is written in the upper boundary register 3, and the minimum memory value in the system is written in the lower boundary register 4. Furthermore, the comparison circuit 6 is set not to perform comparison with the value of the program counter 5.

When starting execution, the program first writes the upper limit of its operating range to the upper limit boundary register 3 and the lower limit to the lower limit boundary register 4, and then sets the comparison circuit 6 to start the comparison function. do. After this setting is performed, the comparator circuit 6 constantly compares the program counter 5 with the contents of the upper and lower boundary registers 3 and 4. When the value of the program counter 5 exceeds the range indicated by the boundary register, the comparator circuit 6 notifies the outside of the situation through the terminal 8, and at the same time notifies the sequencer 7 of this situation.
The function of the comparator circuit 6 is stopped. When the sequencer 7 is notified that the boundary has been crossed, it sets a predetermined special value in the program counter 5, and thereafter starts executing the special program.

FIG. 2 shows the second microprocessor of the present invention.
It is a block diagram showing an example of. In the same figure, the second
This embodiment is obtained by adding a save register 12 that constantly copies and saves the contents of the program counter 5 to the microprocessor of the first embodiment.

The operation of the microprocessor of this embodiment is the same as that of the first embodiment. just,
In this embodiment, boundary values are set for the value of the program counter 5 in the upper and lower boundary registers 3 and 4, and saving in the saving register 12 is started at the same time as the comparison is executed. Further, when the value of the program counter 5 exceeds the boundary, saving is stopped. Therefore, the content of the save register 12 retains the value immediately before the boundary is crossed. Therefore, by checking the contents of this save register 12 using a special program that is executed when the boundary is crossed, it is possible to know from which address in the program the runaway started.

[0014]

As explained above, the present invention provides a register that indicates the range of an operating program, and constantly compares the contents of this register with the contents of the program counter. We made it possible to know from the outside when the limit has been exceeded.
You can find out if the program is running out of control.

Furthermore, since the value of the program counter at this time is held, the address at which the runaway started can be easily known, which has the effect of facilitating debugging of the hardware and program.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing a first embodiment of a microprocessor of the present invention.

FIG. 2 is a block diagram showing a second embodiment of the microprocessor of the present invention.

[Explanation of symbols]

1 Register file 2 Arithmetic circuit 3 Upper bound register 4 Lower boundary register 5 Program counter 6 Comparison circuit 7 Sequencer 8 Terminal 11 Local data bus 12 Save register

Claims (2)

[Claims] 1. A program counter comprising: a first boundary register indicating an upper limit of a program execution range; a second boundary register indicating a lower limit; and a program counter having contents of the first and second boundary registers and a program execution address. and a comparison circuit for comparing values, and during execution of the program, the first
, when the range indicated by the second boundary register is exceeded, a signal indicating the state is outputted to the outside, the execution of the program is stopped, and control is passed to a special program set in advance. microprocessor. 2. The microcontroller according to claim 1, further comprising a register for saving the contents of the program counter immediately before the deviation from the range indicated by the first and second boundary registers. processor.