JPH0228849A - Memory device - Google Patents

Abstract

PURPOSE:To completely eliminate the change of a program even when the necessity of rearrangement is generated by providing one register and one subtracter and setting a free memory space in correspondence to the scale of a system. CONSTITUTION:An arbitrary address is set to a IBP 1 with initial setting. When a ROM goes to be large and the address of the ROM is overlapped with that of a RAM in a present memory map, such a problem can be solved since the enough memory space can be obtained by causing the value of the IBP 1 to be larger than the present value. Even when the RAM goes to be large, the same processing can be executed. Further more, it can be also to wholly arrange a ROM 6, a RAM 5, a register file 4 and an I/O 3 continuously from an address 0. An unnecessary high order address bit can be made unused. By referring the IBP 1 as the register, it is wholly unnecessary to change the program with the change of the value of the IBP 1.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a memory that allows the memory space to be freely rearranged according to the system scale, ROM, and RAM size when determining the memory space in a microprocessor or the like. It is related to the device.

BACKGROUND OF THE INVENTION Traditionally, in microprocessors, memory space is
As shown in the figure, it is fixed at the time of hardware decision,
Later, when it became necessary to expand the ROM and RAM, it was necessary to rearrange the memory space. At this time, the hardware that had been configured up until then had to be rebuilt,
Also, the software had to be rewritten to accommodate the new memory upgrade.

Furthermore, it is also possible to freely set the memory space using a memory management unit (hereinafter abbreviated as MMU). However, the hardware of the MMU itself is quite large, so it is difficult to implement it easily, and even if it were implemented, it would require a lot of initial settings.

Problems to be Solved by the Invention In the above-mentioned conventional system, the memory space is determined, so the expandability of the ROM and RAM is poor, and it is necessary to adapt the program to the size of the system.

Furthermore, when an MMU is used, there are problems in terms of cost and the like because the hardware is large.

Means for Solving the Problems To achieve this object, the present invention has an input/output base pointer or a settable register and a subtractor that subtracts the contents of the register from the address, and the subtracted value is used as a new Each peripheral circuit, memory circuit, etc. can be placed as an address.

Effect: By doing this, you can freely determine the memory space according to the size of the system by just making simple initial settings.

EXAMPLES Hereinafter, examples of the present invention will be described with reference to the drawings.

FIG. 1 is a configuration block diagram in one embodiment of the present invention.

In this figure, 1 is a register (hereinafter abbreviated as IBP) that can be set as an input/output base pointer (IloBP or IBP), 2 is a subtracter that subtracts the value of IBPI from the address, and l103° register file 4 ．． RAM
5 is placed in the memory space using the subtracted value as a new address. Further, the ROM 6 is arranged directly at the address.

First, as an initial setting, an arbitrary address is set in IBPI. An example of the memory map at this time is shown in FIG. ROM6 is located from address O, regardless of IBP, and from l103. Register file 4. The RAM 5 is arranged around the value of IBPI.

Suppose now that because the ROM has become larger, a case has arisen in which addresses overlap with the RAM in the current memory map. The problem can then be solved by increasing the IBPI value to a larger value than the current value, since sufficient memory space can be secured. The same applies when the RAM becomes larger.

Moreover, in this memory map example, ROM6. RAM5
．． Register file 4. It is also possible to arrange all of l103 consecutively starting from address O, and it is also possible to leave unnecessary upper address bits unused. For example 6
If the address fits within 4 bytes, only the lower 16 bits of the address need to be used.

Also, by allowing IBPI to be referenced as a register, l103. IB register file 4 etc.
A program can be created relative to the PI, thereby making it completely unnecessary to change the program by changing the IBPI value.

Effects of the Invention As described above, by providing one register and one subtracter, the present invention allows free memory space to be set according to the scale of the system, and even when relocation is necessary, the program can be changed easily. is all (can be made unnecessary.

[Brief explanation of the drawing]

1...Settable register TBP, 2...
...Subtractor that subtracts the value of IBP from the address, 3...
...Ilo, 4...Register file, 5.
...RAM, 6...ROM.

Claims (1)

[Claims] A memory device that has an input/output base pointer or a configurable register and a subtracter that subtracts the contents of the above register from the address, and can use the subtracted value as a new address to allocate each peripheral circuit and memory circuit. .