JPH0527975A - Microcomputer - Google Patents

Abstract

PURPOSE:To facilitate the transfer of variables such as a sub routine, etc., in a stack by respectively providing first and second micropointers at the data storage places of first and second stack areas on a memory. CONSTITUTION:The stack area on the memory is divided into two areas 5 and 4, data to be used at the hardware of a return destination of the sub routine (SUB) or the return destination of interruption are stored in the place of the first area 5 shown by a first stack pointer SP-1, and data to be used on the software of augument, etc., are stored in the place of the second memory area 4 shown by the second stack pointer. Thus, since the stack is divided by functions even when instructions are alternately continued for operating the data on the hardware and the software, the transfer of variable is made smooth.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a microcomputer, and more particularly to a microcomputer which facilitates the transfer of variables such as subroutines in stack operations.

[0002]

2. Description of the Related Art When a stack operation is performed by a conventional microcomputer, the method shown in FIG. 2 is used. In FIG. 2, 1-3 are steps of a stack operation instruction, 7 is a stack area, SP3 is a stack pointer indicating a data storage location in the stack area, and data and stack when the steps of 1-3 instructions are executed. Indicates a change in pointer

To explain the operation, first, when PUSH α in the first step is executed, the variable “α” is saved in the stack area 7 and the stack pointer SP3 is set to “0”.
Change from 000 ”to“ 0001. ”Next, when the second step PUSH β is executed, the variable“ β ”is saved in the stack area 7 and is stacked on the variable“ α ”. The pointer SP3 indicates “0002”.
Next, when the instruction JSR SUB of the third step is executed and the subroutine (SUB) is called, the data of the return address of the subroutine is further loaded on the variable “β”, and the stack pointer SP3 finally becomes. Indicates "0003".

[0004]

In the conventional microcomputer, data is accumulated in the stack area indicated by the stack pointer. Therefore, if the values of the variables α and β are used in the called subroutine, it is currently impossible to use the values. There is a problem that the address where the data of variables α and β are stored must be calculated from the stack pointer of. For this reason, there is a problem in that it is not easy to pass variables, and the object code of the compiler result of the function calling portion using the C combiner becomes large.

The present invention has been made in order to solve the above-mentioned problems. It is possible to easily pass a variable to a subroutine by a stack, and a compiler result of a function calling portion using a C compiler. The object is to provide a microcomputer that does not increase the object code in.

[0006]

In the microcomputer according to the present invention, the stack area on the memory is divided into a first stack area 5 and a second stack area 4, and
Used in software such as a first stack pointer SP1 indicating a location where data used in hardware such as a return destination of a subroutine in the stack area of the second stack area is stored, and an argument in the second stack area And a second stack pointer SP2 indicating the location where the data is stored.

[0007]

In the microcomputer according to the present invention, the stack area on the memory is divided into two areas, and the data used by the hardware such as the return destination of the subroutine or the return destination of the interrupt is indicated by the first stack pointer. The data is stored in the location of the first memory area, and the data such as an argument used on the software is stored in the location of the second memory area indicated by the second stack pointer. In this way, the place to store the data is divided according to the function of the data to be stored.

[0008]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a diagram showing a stack area and a stack pointer in an embodiment of the present invention. In FIG. 1, 1
˜3 are instruction steps, 4 is a stack area as a first stack area, 5 is a stack area as a second stack area, SP2 is a stack pointer as a second stack pointer, and SP1 is a first stack pointer. Is a stack pointer, which indicates a change in the data in the stack area and a change in the stack pointer depending on the instruction.

The stack area on the memory is divided into two stack areas. The stack area 5 of the first stack area is the return destination of the subroutine (return address of the subroutine) and the return destination of the interrupt destination (address of the interrupt destination). ) And other data used by hardware is stored in the location indicated by the stack pointer SP1. Further, the stack area 4 of the second stack area is a stack for storing the data used on the software of the argument at the location indicated by the stack pointer SP2.

Next, the operation of this embodiment will be described with reference to FIG. When the instruction is not executed, the stack pointer SP2 in the stack area 4 indicates "0100". When the instruction of PUSH α, which is the first step, is executed, the stack pointer SP2 becomes “010
1 ”and the data“ α ”is saved in the stack area 4. Next, when the instruction of PUSH β which is the second step is executed, the stack pointer SP2 is set to“ 0102 ”.
The data “β” is saved in the stack area 4 and stacked on the data “α”.

Next, the third step, JSR SU
When B executes the instruction, this instruction executes the subroutine (S
Since it is an instruction to call UB), the data of the return address of the subroutine is loaded in the location indicated by the stack pointer SP1 "0000" of the separately provided stack area 5, and the stack pointer SP1 is set to "0001". In this way, even when the instructions for manipulating the data on the hardware and the data on the software continue alternately, the stack is divided according to the functions, so that the variables can be passed smoothly.

In this embodiment, an example in which the stack is divided into two has been described, but the number of stacks and the number of stack pointers divided by function are not limited to two, and can be further increased.

[0013]

As described above, according to the present invention, the first stack area indicating the data storage location of the first stack area on the memory is displayed.
, And the second micropointer indicating the data storage location of the second stack area on the memory, it becomes possible to easily pass and receive variables, so that the subroutine is structured and modularized. Also, the object code in the compiler result of the function calling portion using the C compiler is smaller than the conventional one.

[Brief description of drawings]

FIG. 1 is a diagram showing a stack area and a stack pointer according to an embodiment of the present invention.

FIG. 2 is a diagram showing a stack area and a stack pointer in an example of a conventional technique.

[Explanation of symbols]

 4,5 Stack area SP1, SP2 Stack pointer

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[Procedure amendment]

[Submission date] June 4, 1992

[Procedure Amendment 1]

[Document name to be amended] Statement

[Correction target item name] 0004

[Correction method] Change

[Correction content]

[0004]

In THE INVENTION Problems to be Solved by conventional microcomputer, the data in the stack area indicated by the stack pointer is gradually piled, variable α in the called subroutine, if you try to use the value of beta, now There is a problem that the address where the data of variables α and β are stored must be calculated from the stack pointer of. For this reason, there is a problem in that it is not easy to pass variables, and the object code of the compiler result of the function calling portion using the C combiner becomes large.

Claims (1)

Claim: What is claimed is: 1. A stack area on a memory is divided into a first stack area and a second stack area, and is used on hardware such as a return destination of a subroutine in the first stack area. A first stack pointer indicating the location where the data to be stored is stored, and a second stack pointer indicating the location where the data such as an argument in the second stack area used in software is stored. A microcomputer characterized in that.