JPS59183449A - Memory space extending system of microcomputer system - Google Patents

Abstract

PURPOSE:To extend easily a memory space by using an existing microcomputer with addition of a circuit outside of a ready-made microcomputer. CONSTITUTION:When a memory space is extended, the program memory space is allotted to 16 sets of memories (00000) with the RAM space alloted to 16 sets of memories (10000) and (20000) respectively. The instruction which gives accesses to RAM space of each 16 sets of memories (10000) and (20000) is decided among MOVE, LOAD and STORE instructions of an existing microcomputer i- 8085. This decided instruction is registered to an instruction word analysis switch indicating part 205. While an upper address (1) 16 of the 16 sets of memories (10000) is stored to a memory upper address storage part 206 with each pio instruction when an access is given to the 16 sets of memories (10000) for program production. While an address (2) 16 is stored to the part 206 with the pio instruction when an access is given to the 16 sets of memories (20000). Then the memory access is carried out by programming.

Description

[Detailed Description of the Invention] [Subject of the Invention] The present invention relates to a microcomputer system, and particularly to a microcomputer system suitable for easily expanding memory space by using an off-the-shelf microcomputer and adding an external circuit. Regarding the method.

[Background of the invention]

In the conventional memory expansion method, the memory is divided into a basic memory section 1o1 and extended memory sections 102 to 104, as shown in FIG.
There are some that aim to expand the memory space by selecting one.
It is not suitable for expanding the program area. There were drawbacks such as the basic memory space becoming narrower due to the expanded memory space.

[Purpose of the invention]

An object of the present invention is to easily provide a wide memory space by using a ready-made microcomputer and adding an external circuit.

[Shelf of inventions, essential]

A microcomputer constantly repeats reading from or writing to memory (memory access), and which address to access is uniquely determined by the contents of the instruction word. However, if you try to access memory beyond the memory space originally provided by the Microcombi, the address will no longer be uniquely determined by the instruction word, and you will have to add an upper address from outside the Microcombi. Must be. Regarding the addition of higher-order addresses, if the instruction word is analyzed and the upper-order addresses are added according to its contents, it is possible not only to expand the memory space but also to improve system expandability.

[Embodiments of the invention]

An embodiment of the present invention will be described below with reference to FIG.

However, in order to make the explanation more concrete, the microcomputer will be explained using an i-8085 or an equivalent product and its instruction words.

A microcomputer system having this memory expansion includes a microcomputer 201 and an address (ooo
oo), 6~(o F F F FCl2 In addition to the globally accessible memory 202, the address (10000
)+a~(IFFFF)+eAccessible memory 20
3 to (n0000), memory 2 that can be accessed by 6 devices
Expansion memory up to 04, part 205 that further analyzes the command word of the microcomputer and issues an instruction to switch the upper address of the memory, and a part 205 that stores this upper address of the memory according to the p1o command from the microcomputer.
Consists of 6.

Now, when expanding the memory space, the program memory space is (00000) + e memory, and the RAM space is (1).
0000) re memory and (20000)+e memory. Next, MOVE of i-8085,
RAM space (100
Decide the command to be used when accessing the 00) la machine and the (20000) la machine, and change the command word to instruction word 1.
Register in the ψT analysis switching instruction section. Now, if Mnemonic Ll
)AXD-5TAXB, it is decided to access, and each instruction word (l A ) re, (02)+6 is registered. On the other hand, when creating a program, (1oooo), a
When accessing the data, use the pio command (1
0000)Ha is the upper memory address (')la
(20000).

(2) la for each hpiO
Programming is performed so that the memory is accessed after being stored in the memory upper address storage section by a command. To load data from address (12545), , first use the pio instruction to access the upper memory address for LDAXD ('
)+s to the memory, then write (2) to the (DE) register.
345), 6 is stored and then LDAXD is issued. L
The DAXD instruction word (IA)re is read from the program memory space (00000), e-range, but the instruction word analysis switching instruction unit checks whether this instruction word is a pre-registered instruction word. Please check and register (
IA)+6, so the upper memory address is set to LD.
Switch to (1) 16 stored for AXD. l-808
5 sends 6 to the address bus (2345) in order to access e stored in the (DE) register (2345), but since the upper memory address is (')re, the address (12345), , is accessed and the data stored there is read. Similarly, in the case of 5TAXB, the upper address for 5TAXB is
If (2)re is set, this is stored in the memory upper address storage section by the p1o instruction.

Next, store (6789), , in the (+3C) register and issue the 5TAXB command, the address (267a
q) Data is written to la.

Summarizing the above, we will create explanatory diagrams according to the program in sections 5 to 5.
As shown in the figure. Figure $3 shows reading when normal memory expansion is performed and 7f is left. In addition, as shown in Figure 4.5, the upper address for memory read (LDAXl)) and the upper address for memory write (STAX iJ) are set to 1-f. Memory transfer also becomes an RIJ function. In addition to expanding the memory space related to the data mentioned above, the expansion of these memory spaces is due to changes in the instruction word analysis switching instruction section. Furthermore, it can be extended by applying it to the pio instruction.

〔Effect of the invention〕

According to the present invention described above, the memo IJ 2 of a microcomputer can theoretically be expanded infinitely (2), so that the system expandability of microcomputer applications can be dramatically improved.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram of a conventionally known computer system, FIG. 2 is a schematic diagram of an embodiment of the present invention, and FIG.
5 are explanatory diagrams of the system σ) program shown in FIG. 2. 205: Instruction word analysis and memory upper address switching instruction unit; 206: Memory upper address storage unit. Potato 1 illustration

Claims (1)

[Claims] A memory space expansion method for a microcomputer system, characterized in that the microcomputer system includes a microcomputer instruction word analysis, a memory upper address switching section, and a memory upper address storage section in addition to the normal system configuration.