JPH06161810A - Diagnostic system for duplex memory - Google Patents

Abstract

PURPOSE:To turn a standby CPU to a standstill state and to eliminate a system fault caused by the runaway or abnormality of the standby CPU by diagnosing a duplex memory from an active CPU. CONSTITUTION:In a device composed of an active CPU 1, active memory 3, standby CPU 2 and standby memory 4 while duplexing the CPU and the memories, the write addresses of active and standby memories 3 and 4 are made equal for always performing the backup of data. Therefore, the same data are written at the same time. Concerning the read of memories, those memories can be individually accessed by changing the read addresses of active and standby memories 3 and 4. Thus, the duplexed memories 3 and 4 can be accessed and diagnosed from the active CPU 2 by such a system for changing addresses at the time of writing and reading the memories.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention has a CPU and a memory.
It is a memory diagnostic method for a duplicated device.

[0002]

2. Description of the Related Art An active CPU and an active memory, and a standby CPU and a standby memory are paired, and access to the standby memory is possible only from the standby CPU. The diagnosis is performed by the standby CPU.

[0003]

When the standby CPU is diagnosed by the standby CPU, the active CPU and the standby CPU compete with each other at the time of writing the memory, and there is a problem that the system may be down due to an abnormality or runaway of the standby CPU. It was

An object of the present invention is to reduce the risk of system down by prohibiting bus access by putting the standby CPU in a normally stopped state by adopting a method of diagnosing the standby memory from the active CPU.

[0005]

In order to always back up data, the write addresses of the active and standby memories are the same. Therefore, the same data is simultaneously written. The memory read can be individually accessed by changing the read addresses of the active and standby memories. By the method of changing the address at the time of memory write and read, it is possible to access and diagnose the duplicated memory by the active CPU.

[0006]

In the present invention, the memory address at the time of writing and the memory address at the time of reading are decoded and the addresses are changed. As a result, the active memory and the standby memory can be read individually, so that the diagnosis of the duplicated memory can be performed from the active CPU.

[0007]

Embodiments of the present invention will be described below with reference to FIGS. In FIG. 1, 1 is an active CPU, 2 is a standby CPU, 3 is an active memory, and 4 is a standby memory. In FIG. 2, 11 is an address space of the active memory and the standby memory at the time of memory write, 12 is an address space of the active memory at the time of read, and 13 is an address space of the standby memory at the time of read.

Normally, data processing is performed by the active CPU 1 and the active memory 3, and the standby CPU 2 is in a stopped state. At this time, if an abnormality occurs in the active CPU 1 or the active memory 3, the active CPU 1
1 is in a stopped state, and data processing is standby CPU 2
And the standby memory 4 is switched.

When data is written from the active CPU 1, the active memory 3 and the standby memory 4 are simultaneously written. This is because the address when writing to the active memory 3 and the standby memory 4 is the address space 1
It is realized by allocating the same address as 1.

When the active CPU 1 reads data,
This is performed individually from the active memory 3 and the standby memory 4. This is because the read address of the active memory 3 is assigned to the same address as the write address in the address space 12, and the read address of the standby memory 4 is assigned to an address different from the write address in the address space 13. Realized by.

The active CPU 1 writes data to the address space 11, then reads data from the address space 12, compares the write data with the read data, and diagnoses the active memory. Further, the active CPU 1 reads data from the address space 13 to the address space 11. The standby memory is diagnosed by comparing the written data with the read data.

[0012]

As described above, according to the present invention,
By making it possible to diagnose the duplicated memory from the active CPU, the standby CPU can be stopped. As a result, a system failure due to a runaway of the standby CPU or an abnormality is prevented.

[Brief description of drawings]

FIG. 1 is a diagram showing an embodiment of a dual memory diagnostic system according to the present invention.

FIG. 2 is a diagram showing a memory map.

[Explanation of symbols]

 1 ... Active CPU, 2 ... Standby CPU, 3 ... Active memory, 4 ... Standby memory, 11 ... Active during write, standby memory space, 12 ... Active memory space during read, 13 ... Standby memory space during read.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Ryoichi Kurahashi, 1 Horiyamashita, Hinoyamashita, Hadano, Kanagawa Prefecture (72) Shinji Ikezawa, 1st, Horiyamashita, Hadano, Kanagawa (72) Inventor, Fusao Aso, 810 Shimoimaizumi, Ebina, Kanagawa, Ltd., Office Systems Division, Hitachi, Ltd.

Claims (1)

[Claims] 1. A CPU and a memory are duplicated to form an active C.
In an apparatus including a PU and an active memory, a standby CPU and a standby memory, the active C
Memory write from PU consists of a circuit that makes the addresses of the active memory and standby memory the same and performs them simultaneously, and memory read consists of a circuit that performs the addresses individually by changing the addresses of the active memory and the standby memory.
A method of diagnosing a dual memory, wherein the active CPU makes a standby memory accessible so that the active CPU diagnoses the standby memory.