Method and apparatus for storing main data with two checkup data

• US 20030126499A1
• Filed: 11/04/2002
• Published: 07/03/2003
• Est. Priority Date: 12/27/2001
• Status: Active Grant

• Current Assignee: DENSO Corporation
• Original Assignee: DENSO Corporation
• Inventors: Sawamoto, Tetsuo, Miyamoto, Seiji
• Granted Patent: US 7,181,645 B2
• Time in Patent Office: Days
• US Class Current: 714/13
• CPC Class Codes: G06F 11/1008 in individual solid state devices G06F11/1004 takes precedence

Abstract

An electronic control unit has a microcomputer and a backup RAM, which stores its data irrespective of ON/OFF of an engine ignition switch. The backup RAM stores a main data in its storage area, and two checkup data in its storage areas, respectively. The two checkup data are calculated as a two-byte data from the main data of a 4-byte floating points type data and equal to each other. The microcomputer executes a data storing operation in the order of one checkup data, the main data and the other checkup data. The microcomputer determines that the main data is correct when either one of the checkup data is determined correct.

Claims

1. An apparatus comprising:

a backup memory having first, second and third storage areas; and

a microcomputer programmed to calculate a main data and two checkup data, and store the main data and the two checkup data in the first, the second and the third storage areas of the backup memory, respectively,

wherein each of the two checkup data has a data length smaller than that of the main data.

2. The apparatus as in claim 1, wherein the microcomputer stores the main data in the first storage area between storing the two checkup data in the second and the third storage areas.

3. The apparatus as in claim 1, wherein the microcomputer is an n-bit type, and a total length of the main data and the two checkup data is larger than n-bit.

4. The apparatus as in claim 1, wherein the main data is a floating points type, and each data length of the two checkup data is one half of that of the main data.

5. The apparatus as in claim 1, wherein the microcomputer is further programmed to determine whether the main data is correct by comparing at least one of the two checkup data with a third checkup data.

6. A method comprising steps of:

determining a main data;

determining first and second checkup data, each of the checkup data has a data length smaller than that of the main data;

storing the first checkup data in a first checkup data storage area of a backup memory;

storing the main data in a main data storage area of the backup memory after the first checkup data is stored; and

storing the second checkup data in a second checkup data storage area of the backup memory after the main data is stored.

7. The method as in claim 6, further comprising:

reading the main data as well as the first and the second checkup data from the backup memory;

comparing the first and the second checkup data with a predetermined third checkup data; and

determining that the main data is correct if at least one of the first and the second checkup data is equal to the third checkup data.

8. The method as in claim 6, wherein the first and the second checkup data are determined from the main data and are equal to each other.

9. The method as in claim 6, wherein each data length of the first and the second checkup data is one half of that of the main data, and each data length is 2ⁿ bytes with n being variable.

10. The method as in claim 7, wherein the main data is calculated from engine operating conditions, and the third checkup data is calculated from the main data read out from the backup memory.