JPH05113927A - Main storage access system for information processor - Google Patents

Abstract

PURPOSE:To attain a constitution where a microprogram is not required to be cared of even if the change of capacity of a main storage occurs when the accesses are given to the microprogram, a control table, etc., which are stored in the places near the largest address of the main storage. CONSTITUTION:A register (A) 1 is provided to store the size of a main storage together with an adder 2 which adds together the addresses of accesses to be given to the main storage. A code bit is added to the highest order part of the access of the main storage. When this code bit is equal to '1', the value obtained by adding the main storage address to the value of the register (A) 1 is used to the actual address of the main storage. When an access is given to a microprogram or a control table, the highest order bit is set at '1' together with application of the complement of '2' of a relative address of the area to receive an access. Thus the access is possible to the microprogram or the control table with no consciousness of the size of the main storage. (The microprogram and the control table are stored in the addresses of the smaller sizes than the largest address.).

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a main memory access method for an information processing device.

[0002]

2. Description of the Related Art Conventionally, in an information processing device, since the frequency of use of application software and the like is low near the maximum address of the main memory, it is used as a storage area for micro programs, management tables, log data, etc.
It is often the area that cannot be used by software.

When used in this way, a boundary address is set in advance according to the capacity of the main memory, and when accessing this area, the boundary address is used as a base.
The absolute address is generated by adding the boundary address to the relative address in the management area.

[0004]

However, in this conventional method, when the main storage capacity changes, the boundary address also changes. Therefore, each time the storage area is accessed,
Since the absolute address was generated by adding the boundary address to the relative address in the storage area, set the boundary address in the register that is the input of the address adder with a microprogram etc. and store it in the register that is the other input. It is necessary to be aware of it in the microprogram, such as setting the relative address in the table and issuing a command for main memory access, or holding the address to which the boundary address has been added in advance in a work area before using it. Since there is a change in the values such as, there is a problem that it takes a long time to execute, and it is a troublesome place for bugs when designing a microprogram.

Therefore, an object of the present invention is to allow a microprogram to be unaware of accessing the microprogram or management tables stored near the maximum address of the main memory even if the capacity of the main memory changes. There is a point.

[0006]

In order to solve such a problem, the main memory access method of the information processing apparatus of the present invention is such that the contents of the main memory change depending on the use, and a microprogram or a management table for controlling the operation. In an information processing apparatus having a main memory in a main memory, a register for storing the size of the main memory and an adder for adding an address at the time of accessing the main memory are provided, and a sign bit is provided in the most significant bit of the main memory address. , A storage function for storing the microprogram and the management table in a direction in which the address becomes smaller than the maximum address of the main memory, and when accessing the microprogram and the management table, the most significant bit is set to "1" to set the relative address to 2 , And when the most significant bit is “1”, the register A and the main memory address are added by the adder. It is obtained by an adding function of.

[0007]

Embodiments of the present invention will now be described with reference to the drawings. FIG. 1 is a block diagram of hardware for implementing the main memory access method of the present invention.

In the figure, 1 is {main memory size-1}.
Is a register A for storing the address, 2 is an address adder, and 3 is a selector for selecting the output of the address adder 2 and the absolute address 1. The selector 3 selects the output of the address adder 2 when the most significant bit of the absolute address 1 is "1". The data input path is for setting the value to register A.

That is, this hardware has a register A1 for storing the size of the main memory and an address adder 2 for adding the address at the time of access to the main memory, and the code is placed in the most significant bit of the main memory address. A bit is provided to store the microprogram and the management table in a direction in which the address becomes smaller than the maximum address of the main memory, and when accessing the microprogram and the management table, the most significant bit is set to "1" to set the relative address. Given in 2's complement, when the most significant bit is "1",
The adder has an adding function for adding the register A and the main memory address, and is used as an actual main memory access address.

FIG. 2 shows a map of the main memory. The size of (1) is 64 Kbytes. The size of (2) is 1 MB. Therefore, the value of the register A is set to "OFFFF" in the case where the main memory is shown in FIG. 2A, and is set to "FFFFF" in the case of (2) through the data input path. The setting of the value of the register A is performed as one of the initial settings performed after the system power is turned on. The shaded area is an area in which micro programs, management tables, etc. are stored. The size of this area is constant regardless of the main memory size.

In the embodiment, since the main memory size is 1 Mbyte at maximum, the absolute address 1 has a width of 21 bits and the absolute address 2 has a width of 20 bits. FIG. 3 shows the correspondence between the address given to the absolute address 1 and the absolute address 2 which is actually the address of the main memory.

In FIG. 2, an arrow is added to a portion corresponding to FIG. As is clear from FIGS. 2 and 3, in the case of, the value of the absolute address 2 corresponding to the absolute address 1 is different. From now on, when accessing the shaded area in FIG. 2, the value given to the absolute address 1 may be given as the two's complement of the relative address of the shaded area, regardless of the main memory size.

As a result, even if the main storage capacity changes depending on the use, it is possible to access without being aware of the physical address where the microprogram and the management table are stored.

[0014]

As described above, according to the main memory access method of the information processing apparatus of the present invention, it is possible to access the storage area set in the upper address part of the main memory when the main memory size changes. Since it is not necessary to be aware of the change in the address of the storage area due to the change in the main memory size, no extra time is required for processing such as changing the value of the base register, and the complexity of microprogram design is reduced. There is an effect.

[Brief description of drawings]

FIG. 1 is a block diagram showing hardware that realizes a main memory access method of an information processing apparatus according to an embodiment of the present invention.

FIG. 2 is a diagram showing an example of a main memory map.

FIG. 3 is a diagram showing correspondence between addresses.

[Explanation of symbols]

1 Main memory size storage register A 2 Address adder 3 Address selector 4 Absolute address 1 (21 bit width) 5 Absolute address 2 (20 bit width) 6 Data input path (1) Main memory map (64 Kbytes) Address register (2 ) Main memory map (1 MB) address register

Claims (1)

[Claims] 1. In an information processing device having a main program, which has a microprogram for controlling operations and a management table, the contents of the main memory change depending on the use, and a register for storing the size of the main memory and a register for accessing the main memory. A storage function that has an adder for adding an address, a sign bit is provided in the most significant bit of the main memory address, and the microprogram or the management table is stored in a direction in which the address becomes smaller than the maximum address of the main memory, When accessing the microprogram or the management table, the most significant bit is set to "1" and the relative address is given in 2's complement. When the most significant bit is "1", the adder adds the register and the main address. A main memory access method for an information processing apparatus, comprising: an addition function for adding storage addresses.