JPS62219126A - Program control system - Google Patents

Abstract

PURPOSE:To easily debug while a program is compared by eliminating the need for changing and correcting the program which comes to be an origin at the time of a part of the program is changed, and selecting whether or not the changed program is effective, only by setting a flag. CONSTITUTION:A program counter 2 outputs the address of a control memory 1 storing a program step to branch to the changed program stored in an address register 3. Then, a comparator 5 generates a coincident output. When the flag output of a flag register 4 to show that the changed program is effective exists, the special address of the control memory 1 to store the head address of the program changed from the program counter 2 by the coincident output is outputted. By executing such a control, the changed program is successively executed in which the address stored in the special address of the control memory is a head address.

Description

[Detailed Description of the Invention] [Summary] In a processing device using a program sequential execution method in which a program stored in a control memory is sequentially read out and executed according to an address from a program counter, the starting address of a changed program is Store at a specific address in the above control memory and if this modified program is valid when the address from the program counter matches the address that should branch to this modified program. The above program counter is now set.

[Industrial application field]

In the program sequential processing method in which the program is sequentially read from the control memory and executed at an address determined by a program counter that is incremented by one each time one step of the program is processed, especially when the program counter is It provides an effective program control device.

[Conventional technology]

In an information processing device that uses program sequential execution, the program to be processed is stored in a one-dimensional control memory, so if you try to use a longer program than the original program when changing part of the program, Not only does it require a large storage area, but it also requires modification of steps that do not originally require modification, such as the destination address of a branch instruction, as it becomes necessary to change the address of the subsequent program.

Also, one way to eliminate this drawback is to write the program to be updated into a free area in the control memory, and write an instruction with the address of this updated program as the destination in the original program. Branching has been done, but if it is necessary to re-execute the program before the change, a program is needed to return to the original program.

Furthermore, if these programs are on read-only memory (hereinafter referred to as ROM), it is impossible to modify them as they are, so some of the contents of this ROM are moved to random access memory (hereinafter referred to as RAM). I was debugging the program from ROM to R.
A means to switch to AM was required.

[Problem that the invention seeks to solve]

The present invention eliminates the drawbacks of the prior art as described above and provides a program control device that facilitates branching to a modified program and returning to the original program without using this modified program. That is.

[Means for solving problems]

As shown in the principle diagram in Figure 1, the start address of the changed program is stored at a specific address in the control memory (1), and a flag is stored that indicates that the updated program is valid. Register (4
), and an address register (3) for storing the start address of the changed program in the original program;
A comparator (5) that compares the address from the program counter (2) with the address from the address register, and the condition that the flag exists when the comparator detects a match between the two addresses. The program counter (2) is set to a specific address in the control memory (1) that stores the start address of the changed program.

[For production]

When the program counter (2) outputs the address of the control memory (1) containing the program step that branches to the modified program stored in the address register (3), the comparator (5) outputs a match. occurs,
If there is a flag output from the flag register (4) indicating that this modified program is valid,
The program counter (2) is set to output a specific address in the control memory (1) that stores the starting address of the program changed by the matching output.

By performing such control, the modified program is sequentially executed with the address stored at a specific address in the control memory as the start address.

Further, by setting the flag in the flag register (4) to indicate that the changed program is invalid, it is possible to cause the original program to perform processing.

In addition, when using a plurality of modified programs, the address register (3) is made to be able to store the first address of branching to the plurality of modified programs, and the comparator (5) It identifies and outputs which branch address matches the address from the program counter (2), and stores the start address of the changed program corresponding to this branch address in accordance with this branch address. The address of control memory (1) may be set in the program counter.

Also, if you need to return to the original program,
A branch instruction containing the address of the next instruction to be executed in the original program may be added to the last step of the changed program.

〔Example〕

FIG. 2 shows an embodiment of the present invention, in which the program counter 2 that specifies the read address of the control memory 1 has its counted value incremented by 1 by the program sequential execution control circuit 11 every time one step of the program is read. The programs in the control memory 1 are sequentially read out and executed.

In the control memory address map shown in FIG. 3, program A is the original program at address $000.
It is assumed that the data is stored in a storage area from $0 to $1000, and normally read out sequentially from $0000 to $1000 according to the address from the program counter 2 mentioned above.

When changing the program step X stored in the area of address $0A00 to $0AFF of program A in the control memory, the changed program The storage area is shown as $EOOO to $EFFF.

At the same time, the address register 3 stores the start address $0AOO of the changed area X of program A that branches to this changed program X', and the address $FFFO stores the start address $E000 of the changed program X'. Store branch instructions.

When the address from the program counter 2 now matches the address $0A00 stored in the address register 3, the comparator 5 produces a match output, and a flag is set in the flagless register 4 indicating that this modified program X' is valid. When set, the AND gate 12 supplies an output to the program sequential execution control circuit 11 and sets the program counter 2 to send out the address output of $FFFO.

As a result, the modified program X is stored in the control memory.
A branch instruction to the start address $EO00 of ' is read,
Since the program counter 2 is subsequently incremented by 1 each time a step of this program is read, processing according to this modified program X' is executed.

If a branch instruction to address $0BOO is written to address $EFFF, which is the last step of this modified program Since the program A is read out and thereafter executed again, a process is executed in which part X of the program A is replaced by the modified program X'.

In the above operation, if the flag in flag register 4 is set to indicate that this modified program The +1 addition by the circuit 11 outputs the address from $0AFF to $0BOO, and program A is executed without being changed.

If you also want to change the program Y stored in $0EOO, $0EOQ, and $0EFF of this control memory, you can change this changed program Y' to, for example, $0EOO to $0EOQ to $0EFF.
Store in DOOO or $DOFF and $FFF
1 stores a branch instruction to $DOOO, and is provided with a device consisting of an address register 31, a flag register 41, a comparator 51, and an AND gate 13, which correspond to an address register 3, a flag register 4, a comparator 5, and an AND gate 12. , if the program sequential execution control circuit 11 is controlled to output the address $FFF1 from the program counter (2) by the output of the AND gate 13, then
Part of program A can be changed in the same way as described for the replacement of programs X and X'.

Also, programs X and X', and programs Y and Y'
If only one of the replacements is to be performed, only the branch destination address of the address $FFFO in control memory 2 that stores the start address of the changed program is replaced with $E.
It is only necessary to rewrite them to O00 and $DO00, and it is clear that this is the same no matter how many instructions are changed.

〔Effect of the invention〕

When making a partial change to a program, there is no need to change or modify the original program (also, you can select whether or not to make the changed program valid just by setting a flag, so you can compare programs. It is easy to debug while doing so.

Further, since it is possible to select and execute a plurality of changed programs by setting the above-mentioned flags or rewriting the branch destination address, the scope of its use is extremely wide.

[Brief explanation of drawings]

FIG. 1 shows a principle of the present invention, FIG. 2 shows an embodiment of the invention, and FIG. 3 shows an example of a memory map of a control memory. ■...Control memory, 2...Program counter, 3
...Address register, 4...Flag register, 5
. . . Comparator, 6 . . . Program counter cent means.

Claims (1)

[Claims] In a program control device that sequentially reads and executes instructions from a control memory (1) according to an address indicated by a program counter (2), an address register (3) stores the start address of a changed program. and a flag register (4) that stores a flag indicating whether the modified program is valid or not, and a comparison that compares the address from the program counter (2) with the address from the address register (3). means (5) for setting the program counter (2) to the address of the control memory (1) in which the starting address of the program changed by the matching output of the comparator is stored;
6) A program control device comprising: