JPH0520184A - Memory access device - Google Patents

Abstract

(57) [Abstract] [Purpose] An object is to provide a memory access device capable of accessing an extended memory at high speed without arithmetic processing. [Structure] The address value of the space of the extended memory 7 to be accessed is set from the CPU 4 to the extended memory address register 5 and held, and the request register 6 is the extended memory address register during the period when the CPU 4 sets the access request in the request register 6. The address value held in 5 is set in the extension memory 7. The CPU 4 directly specifies the address value of the extended memory to execute the input / output of data, and the address value calculation in the bank system is unnecessary.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a memory access device for accessing data in an extended memory, which is frequently used in English typewriters, at high speed.

[0002]

2. Description of the Related Art In recent years, since an English typewriter has a word processor function and a dictionary function, it is necessary to manage and access a memory which is tens of times the memory space of a CPU. In this case, the memory space is expanded to the outside of the CPU and accessed according to a certain algorithm.

Conventionally, in many English typewriters,
A bank access method is used as a method for accessing the expanded memory. In addition, the English typewriter is compatible with sophisticated and complex software,
A plurality of bank memory spaces having different sizes are provided in the CPU memory space, and the same memory in the extended memory space can be accessed from the plurality of bank memory spaces. Therefore, there are a plurality of sets of bank numbers and addresses in the CPU memory space for the 1-byte extension memory, and it is difficult to manage the extension memory by the bank numbers and the addresses in the CPU memory space. . Therefore, it is managed by using an extension memory address that is uniquely determined by software, and when accessing the extension memory, the bank number corresponding to the bank memory space used for access from the extension memory address and the address in the CPU memory space are stored. I ask for it each time.

A conventional access device for accessing text and dictionary data in the expansion memory according to the bank system will be described below. FIG. 3 is a block diagram showing the configuration of a memory access device for accessing text and dictionary data in an extended memory by the conventional bank method. In the figure, 1 is a CPU, 2 is a bank register in which a target memory address is present, and a bank register for outputting an upper address portion (extended address) of the target memory address to an extended memory, and 3 is an extended register. It is a memory. The extension address is obtained by multiplying the bank number by the bank size. FIG. 2 is a schematic diagram showing the relationship among the extended memory space, the CPU memory space, and the memory space of the bank register.
In the figure, A is the target address to be accessed, B is the bank number of the bank in which the target address A exists, C is the size of the bank, D is the offset address of the target address A, and E is the bank memory in the CPU memory space. The start address of area 0, F is the sum of D and E. Due to the above memory space address relationship, the target address A is represented by A = B × C + D.

When attempting to access the target address A, first the target address A is divided by the bank size C, and the quotient B obtained by the division is the bank number B in which the target address A exists. When the number B is set, the memory area of the bank number B in the extended memory space is cut out to the bank memory area in the CPU memory space. Also, the remainder D obtained by dividing the target address A by the bank size C is the start address of the memory area of the bank number B in the extended memory space, which is 0.
Is the offset address of the target address A in the case of. Therefore, when the bank number B is set in the bank register and then F obtained by adding E to the offset address D is accessed from the CPU, the memory A in the extended memory space is accessed.

[0006]

Since it is necessary to perform operations such as division and addition for obtaining the corresponding address in the bank area from such conventional extended addresses, the load on the software is large and further time consuming. There was a problem.

SUMMARY OF THE INVENTION The present invention solves the above problems, and an object of the present invention is to provide a memory access device capable of accessing an expanded memory at high speed without performing complicated arithmetic processing.

[0008]

In order to achieve the above object, the present invention provides an extended memory address register for inputting and holding an address value in an extended memory space to be accessed from a CPU, and an access request input of the CPU. The memory access device is provided with a request register for setting the address value held in the extension address register in the extension memory during the period.

[0009]

According to the present invention, in the above configuration, when the CPU requests access to the request register, the address of the extension memory held in the extension memory address register is set in the extension memory.

[0010]

【Example】

(Embodiment 1) A memory access device according to an embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram showing the configuration of a memory access device according to an embodiment of the present invention. In the figure, 4 is CP
U and 5 are extended memory address registers that set an address on the extended memory and output the extended memory address set to the extended memory when the CPU accesses the request register. It is composed of the same number of bits. 6 is a CPU
The request register 7 for instructing the extended memory address register to output the extended memory address that has been set during the period of being accessed from the extended memory 7 is an extended memory.

The mutual relationship and operation of the above components will be described below. An address A in the extended memory space is set in the extended memory address register 5. After that, when the request register 6 is accessed, the extended memory address A is output from the extended memory address register and the target address A is accessed while the CPU is accessing the request register 6 to the extended memory address. It will be.

As described above, according to the memory access apparatus of the embodiment of the present invention, the extended memory address register for inputting and holding the address value in the extended memory space to be accessed from the CPU, and during the access request input of the CPU. By providing a memory access device having a request register for setting the address value held in the extension address register in the extension memory, the extension memory can be set by simply accessing the request register in which the extension memory address is set in the extension memory address register. Since it is possible to access and it is not necessary to add operations such as division and addition to the extended address, the number of steps of the program can be reduced, and an extended memory access device that can access the extended memory at high speed can be obtained.

[0014]

As is apparent from the above embodiments, the extended memory address register for inputting and holding the address value in the extended memory space to be accessed from the CPU, and the extended address during the access request input of the CPU. By using a memory access device that has a request register that sets the address value held in the register in the extension memory, you can access the extension memory just by accessing the request register that is set in the extension memory address register, division to the extension address, Since it is not necessary to add operations such as addition, the number of steps of the program can be reduced, and an extended memory access device that can access the extended memory at high speed can be obtained.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of a memory access device according to an embodiment of the present invention.

FIG. 2 is a schematic diagram showing a relationship between memory spaces in a conventional memory access device.

FIG. 3 is a block diagram showing a configuration of a conventional extended memory access device.

[Explanation of symbols]

 4 CPU 5 Extended memory address register 6 Request register 7 Extended memory A Address value to access in extended memory space

Claims (1)

Claim: What is claimed is: 1. An extended memory address register for inputting and holding an address value in an extended memory space to be accessed from a CPU, and the extended address register for holding an access request of the CPU. A memory access device having a request register for setting an address value in an extended memory.