Memory management for unifying memory cell conditions by using maximum time intervals

• US 9,021,181 B1
• Filed: 09/14/2011
• Issued: 04/28/2015
• Est. Priority Date: 09/27/2010
• Status: Active Grant

• Current Assignee: Apple Inc.
• Original Assignee: Apple Inc.
• Inventors: Rotbard, Barak, Meir, Avraham
• Primary Examiner(s): KIM, HONG CHONG
• Application Number:
  US13/231,963
• Time in Patent Office: 1,322 Days
• Field of Search: 711/103, 711/170, 711/173, 713/500, 714/721, 365/233, 365/233.1
• US Class Current: 711/103
• CPC Class Codes: G06F 11/076 by exceeding a count or rate limit, e.g. word- or bit count limit
• CPC Class Codes: G06F 12/0246 in block erasable memory, e.g. flash memory
• CPC Class Codes: G06F 2212/7202 Allocation control and policies
• CPC Class Codes: G06F 2212/7207 management of metadata or control data
• CPC Class Codes: G06F 3/0679 Non-volatile semiconductor memory device, e.g. flash memory, one time programmable memory [OTP]
• CPC Class Codes: G11C 16/10 Programming or data input circuits
• CPC Class Codes: G11C 16/349 Arrangements for evaluating degradation, retention or wearout, e.g. by counting erase cycles
• CPC Class Codes: G11C 7/22 Read-write [R-W] timing or clocking circuits; Read-write [R-W] control signal generators or management

Abstract

A method includes accepting data for storage in a memory that is partitioned into multiple memory regions. A memory region is selected for storing the data. At least part of the data is stored in the selected memory region, subject to verifying that all the storage operations applied to the selected memory region are performed within a predefined maximum time interval.

Claims

1. A method, comprising:

accepting data for storage in a memory device, wherein the memory device is partitioned into a plurality of memory regions and wherein each memory region is partitioned into a plurality of memory pages;

selecting a given memory region;

storing a first part of the data in a first memory page of the given memory region, wherein storing the first part of the data includes performing at least a first write operation on the first memory page;

recording a time stamp, wherein the time stamp is indicative of a time when the at least first write operation is applied to the first memory page;

storing a second part of the data in a second memory page of the given memory region responsive to determining that a difference between a current time and the time stamp is less than a predefined maximum time interval; and

closing the given memory region to additional write operations upon detecting that the predefined maximum time interval has expired since storing the first part of the data, wherein the given memory region includes storage space that is available for storage when closed.

2. The method according to claim 1, further comprising, when a remaining portion of the data is still pending for storage after the given memory region is closed to the additional write operations, storing the remaining portion of the data in another memory region different from the given memory region.

3. The method according to claim 1, further comprising storing other data in the available storage space of the given memory region before the predefined maximum time interval has expired since storing the first part of the data.

4. The method according to claim 1, further comprising:

calculating a respective set of storage parameters that are applicable to all the memory pages in the given memory region; and

storing the respective set of storage parameters in the memory device.

5. The method according to claim 4, wherein the memory device comprises non-volatile memory cells, and wherein calculating the respective set of storage parameters comprises defining a set of read threshold voltages for reading the non-volatile memory cells in the given memory region.

6. The method according to claim 4, wherein calculating the respective set of storage parameters comprises computing the set of storage parameters based on only a partial subset of the plurality of memory pages in the given memory region.

7. The method according to claim 6, wherein the partial subset comprises a single memory page.

8. An apparatus, comprising:

an interface configured to accept data for storage in a memory device wherein the memory device is partitioned into a plurality of memory regions and wherein each memory region is partitioned into a plurality of memory pages;

a timer configured to measure a predefined maximum time interval; and

storage circuitry configured to;

select a given memory region;

perform at least a first programming operation to store a first part of the data in a first memory page of the given memory region;

start the timer at a time corresponding to performing the at least first programming operation;

store a second part of the data in a second memory page of the given memory region responsive to a determination that the timer; and

close the given memory region to additional write operations upon detecting that the timer has expired, wherein the given memory region includes storage space that is available for storage when closed.

9. The apparatus according to claim 8, wherein, when a remaining portion of the data is still pending for storage after the given memory region is closed to the additional write operations, the storage circuitry is further configured to store the remaining portion of the data in another memory region.

10. The apparatus according to claim 8, wherein the storage circuitry is further configured to store other data in the available storage space of the given memory region before the timer expires.

11. The apparatus according to claim 8, wherein the storage circuitry is further configured to:

calculate a respective set of storage parameters that are applicable to all the memory pages in the given memory region; and

store the respective set of storage parameters in the memory device.

12. The apparatus according to claim 11, wherein the memory device comprises non-volatile memory cells, and wherein the respective set of storage parameters comprises a set of read threshold voltages for reading the non-volatile memory cells in the given memory region.

13. The apparatus according to claim 11, wherein the storage circuitry is configured to calculate the respective set of storage parameters based on only a partial subset of the plurality of memory pages in the given memory region.

14. The apparatus according to claim 13, wherein the partial subset comprises a single memory page.

15. An apparatus, comprising:

a memory device, which is partitioned into a plurality of memory regions, wherein each memory region is partitioned into a plurality of memory pages; and

storage circuitry configured to;

accept data for storage in the memory device;

select a given memory region;

perform at least a first programming operation to store a first part of the data in a first memory page of the given memory region;

record a time stamp, wherein the time stamp is indicative of a time when the at least first programming operation is applied to the first memory page;

compare a current time to the recorded time stamp;

store a second part of the data in a second memory page of the given memory region responsive to a determination that a difference in time between the current time and the recorded time stamp is less than a predefined maximum time interval; and

close the given memory region to additional write operations upon detecting that the predefined maximum time interval has expired since storing the first part of the data, wherein the given memory region includes storage space that is available for storage when closed.

16. The apparatus according to claim 15, wherein, when a remaining portion of the data is still pending for storage after the given memory region is closed to the additional write operations, the storage circuitry is further configured to perform at least a third write operation in another memory region for storing the remaining portion of the data.

17. The apparatus according to claim 15, wherein, the storage circuitry is further configured to store other data in the given memory region in the storage space that is available for storage before the predefined maximum time interval has expired since storing the first part of the data.