MEMORY REFRESHING APPARATUS AND METHOD FOR MEMORY REFRESH

• US 20100106901A1
• Filed: 01/06/2010
• Published: 04/29/2010
• Est. Priority Date: 07/18/2007
• Status: Active Grant

• Current Assignee: Fujitsu Limited
• Original Assignee: Fujitsu Limited
• Inventors: HIGETA, Masanori, Sasaki, Takatsugu, Suzuki, Kenji
• Granted Patent: US 8,549,366 B2
• Time in Patent Office: Days
• US Class Current: 711/106
• CPC Class Codes: G06F 11/106 Correcting systematically all correctable errors, i.e. scrubbing
• CPC Class Codes: G11C 11/401 forming cells needing refreshing or charge regeneration, i.e. dynamic cells
• CPC Class Codes: G11C 11/406 Management or control of the refreshing or charge-regeneration cycles
• CPC Class Codes: G11C 2029/0409 Online test
• CPC Class Codes: G11C 2211/4061 Calibration or ate or cycle tuning
• CPC Class Codes: G11C 29/028 with adaption or trimming of parameters
• CPC Class Codes: G11C 29/50016 of retention
• CPC Class Codes: G11C 29/52 Protection of memory contents; Detection of errors in memory contents

Abstract

The optimization of a refresh cycle is carried out in harmony with the error occurrence state in the memory with the presence of a normal patrol controlling section controlling a normal patrol operation that patrols the memory; an additional patrol controlling section controlling an additional patrol operation that patrols, if a first error in the memory is detected during the normal patrol operation, an error occurring area in which the first error occurs and which is included in the memory; a measuring section (15) measuring, if a second error is detected in the error occurring area during the additional patrol operation, an error frequency representing information of error in the error occurring area; and a refresh cycle adjusting section adjusting the refresh cycle in accordance with the error frequency measured by the measuring section.

Claims

1. A memory refreshing apparatus for refreshing a memory at a refresh cycle, comprising:

a normal patrol controlling section controlling a normal patrol operation that patrols the memory;

an additional patrol controlling section controlling an additional patrol operation that patrols, if a first error in the memory is detected during the normal patrol operation performed by the normal patrol controlling section, an error occurring area in which the first error occurs;

a measuring section measuring, if a second error is detected in the error occurring area during the additional patrol operation performed by the additional patrol controlling section, an error frequency representing information of error in the error occurring area; and

a refresh cycle adjusting section adjusting the refresh cycle in accordance with the error frequency measured by the measuring section.

2. The memory refreshing apparatus according to claim 1, wherein the refresh cycle adjusting section stepwisely shortens the refresh cycle if the error frequency measured by the measuring section increases while stepwisely lengthens the refresh cycle if the error frequency measured by the measuring section decreases.

3. The memory refreshing apparatus according to claim 1, wherein the measuring section measures, as the error frequency, the number of errors in the error occurring area per predetermined time period.

4. The memory refreshing apparatus according to claim 1, wherein, if a plurality of the error occurring areas are detected during the additional patrol operation performed by the additional patrol controlling section, the measuring section measures, as the error frequency, the number of the error occurring areas.

5. The memory refreshing apparatus according to claim 1, wherein the refresh cycle adjusting section adjusts the refresh cycle to a predetermined lower limit or more.

6. The memory refreshing apparatus according to claim 5, wherein the refresh cycle adjusting section varies the lower limit on the basis of an access frequency to the memory.

7. The memory refreshing apparatus according to claim 5, wherein the refresh cycle adjusting section varies the lower limit on the basis of memory temperature representing the temperature of the memory.

8. The memory refreshing apparatus according to claim 5, wherein the refresh cycle adjusting section resets the refresh cycle to a default value when an elapsed time passing since the first error is detected in the normal patrol operation performed by the normal patrol controlling section exceeds a predetermined time period.

9. The memory refreshing apparatus according to claim 1, further comprising a monitoring interval varying section varying a monitoring interval of the additional patrol operation on the basis of the refresh cycle adjusted by the refresh cycle adjusting section.

10. The memory refreshing apparatus according to claim 9, wherein the monitoring interval varying section lengthens the monitoring interval when the error frequency measured by the measuring section becomes constant.

11. A method for refreshing a memory at a refresh cycle, comprising the steps of:

controlling a normal patrol operation that patrols the memory;

controlling an additional patrol operation that patrols, if a first error in the memory is detected during the normal patrol operation performed in the normal patrol controlling step, an error occurring area in which the first error occurs;

measuring, if a second error is detected in the error occurring area during the additional patrol operation performed in the additional patrol controlling step, an error frequency representing information of error in the error occurring area; and

adjusting the refresh cycle in accordance with the error frequency measured in the measuring step.

12. The method for refreshing a memory according to claim 11, wherein in the refresh cycle adjusting step, the refresh cycle is stepwisely shortened if the error frequency measured in the measuring step increases while the refresh cycle is stepwisely lengthened if the error frequency measured in the measuring step decreases.

13. The method for refreshing a memory according to claim 11, wherein in the measuring step, the number of errors in the error occurring area per predetermined time period is measured as the error frequency.

14. The method for refreshing a memory according to claim 11, wherein, if a plurality of the error occurring areas are detected during the additional patrol operation performed in the additional patrol controlling step, the number of the error occurring areas is measured as error frequency in the measuring step.

15. The method for refreshing a memory according to claim 11, wherein in the refresh cycle adjusting step, the refresh cycle is adjusted to a predetermined lower limit or more.

16. The method for refreshing a memory according to claim 15, wherein in the refresh cycle adjusting step, the lower limit is varied on the basis of an access frequency to the memory.

17. The method for refreshing a memory according to claim 15, wherein in the refresh cycle adjusting step, the lower limit is varied on the basis of memory temperature representing the temperature of the memory.

18. The method for refreshing a memory according to claim 15, wherein in the refresh cycle adjusting step, the refresh cycle is reset to a default value when an elapsed time passing since the first error is detected in the normal patrol operation performed in the normal patrol controlling step exceeds a predetermined time period.

19. The method for refreshing a memory according to claim 11, further comprising the step of varying a monitoring interval of the additional patrol operation on the basis of the refresh cycle adjusted in the refresh cycle adjusting step.

20. The method for refreshing a memory according to claim 19, wherein in the monitoring interval varying step, the monitoring interval is lengthened when the error frequency measured by the measuring section becomes constant.