Method for storing and retrieving data in a control system, in particular in a motor vehicle

• US 6,167,338 A
• Filed: 09/15/1998
• Issued: 12/26/2000
• Est. Priority Date: 09/15/1997
• Status: Expired due to Fees

• Current Assignee: Siemens AG
• Original Assignee: Siemens AG
• Inventors: De Wille, Eberhard, Ulm, Michael
• Primary Examiner(s): Cuchlinski, Jr., William A.
• Assistant Examiner(s): ARTHUR JEANGLAUDE, GERTRUDE
• Application Number:
  US09/154,152
• Time in Patent Office: 833 Days
• Field of Search: 701/29, 701/35, 701/51, 701/54, 701/57, 477/34, 477/99, 477/101, 707/100, 707/101, 707/200, 707/205, 711/153, 711/171, 711/202, 711/209
• US Class Current: 701/51
• CPC Class Codes: G06F 8/654 using techniques specially adapted for alterable solid state memories, e.g. for EEPROM or flash memories
• CPC Class Codes: G11C 7/20 Memory cell initialisation circuits, e.g. when powering up or down, memory clear, latent image memory

Abstract

The method is used to store and retrieve data in a control system, in particular in a motor vehicle, which contains a computer, a RAM memory and a flash memory. When the control system is switched off, operational data of different types, which can change while the control system is operating and which are required again after the control system is switched on again and which are stored in the RAM memory, are then stored in the flash memory. The flash memory is managed by means of a circular buffer method and can hold multiple copies of the operational data of the same type. When the control system is switched on, the most recent operational data of a respective type of data are determined and output to the RAM memory.

Claims

1. A method for storing and retrieving operational data in a control system having a RAM memory and a flash memory, the method comprising.

switching on the control system;

supplying a backup value for only some of the operational data in the control system; and

storing each backup value in the RAM memory, without accessing the flash memory;

subsequently

obtaining most recent operational data of at least one data type from the flash memory; and

storing the most recent operational data of the at least one data type in the RAM memory.

2. The method according to claim 1, wherein:

the obtaining step comprises obtaining a plurality of data types from the flash memory; and

the step of storing the most recent operational data comprises storing the plurality of data types in the RAM memory.

3. The method according to claim 2, comprising setting at least one pointer to indicate a position and the data type stored in the RAM memory for each respective one of the operational data.

4. The method according to claim 1, comprising:

switching off the control system;

checking if any of the operational data in the RAM memory has been changed subsequent to the step of switching on the control system; and

if any of the operational data in the RAM memory has been changed subsequent to the step of switching on the control system;

subsequently

storing in the flash memory, the operational data in the RAM memory which has been changed subsequent to the step of switching on the control system.

5. The method according to claim 1, comprising:

associating the operational data with a header characterizing the data type; and

storing the operational data and the header in the flash memory.

6. The method according to claim 1, comprising using the control system to control a component in an automobile.

7. The method according to claim 1, which comprising using the control system to control an automatic transmission.

8. The method according to claim 1, comprising:

dividing the flash memory into a plurality of segments;

switching off the control system;

storing the operational data in one of the plurality of segments without writing over previously stored operational data;

subsequently

when the segment becomes full, storing the operational data in a next one of the plurality of segments.

9. The method according to claim 8, comprising associating each one of the plurality of segments with a code indicating whether the respective segment is full, partially full, or empty.

10. The method according to claim 1, comprising:

after at least some of the plurality of segments have been filled;

clearing a segment which has been filled and defining this segment as a cleared segment; and

copying operational data from one of the plurality of segments into the cleared segment.

11. The method according to claim 10, wherein the operational data is unchanging data necessary for operating the control system.

12. The method according to claim 8, comprising after the step of storing the operational data in the next one of the plurality of segments:

switching on the control system; and

searching for the most recent operational data in a currently activated segment.

13. The method according to claim 12, comprising:

if all types of the most recent operational data are not found in the searching step, searching a deactivated segment for previous values of operational data not found.

14. The method according to claim 1, comprising:

subsequent to the obtaining step, checking an integrity of the operational data; and

if an error is found during the integrity check;

subsequently

searching the flash memory for earlier values of intact operational data of the same data type.

15. The method according to claim 1, comprising:

dividing the flash memory into virtual blocks;

finding an empty one of the virtual blocks by checking the flash memory on a block by block basis; and

setting a pointer pointing to the empty one of the virtual blocks.

16. The method according to claim 1, comprising:

switching off the control system;

searching for the most recent operational data contained in the RAM memory;

forming data blocks by combining the most recent operational data;

providing the data blocks with a respective code indicating the data type; and

storing the data blocks with the respective code in the flash memory.

17. The method according to claim 16, which comprising before the storing step, determining the total amount of data to be stored in the flash memory.