Methods and systems for monitoring write operations of non-volatile memory

• US 8,751,903 B2
• Filed: 07/26/2010
• Issued: 06/10/2014
• Est. Priority Date: 07/26/2010
• Status: Active Grant

• Current Assignee: Apple Inc.
• Original Assignee: Apple Inc.
• Inventors: Byom, Matthew, Wakrat, Nir J.
• Primary Examiner(s): GUYTON, PHILIP A
• Application Number:
  US12/843,463
• Publication Number:
  US 20120023365A1
• Time in Patent Office: 1,415 Days
• Field of Search: 714/42, 714/718, 714/763, 714/773, 365/200
• US Class Current: 714/773
• CPC Class Codes: G06F 11/073 in a memory management context, e.g. virtual memory or cache management memory management G06F12/00; testing of static memory units G11C29/00
• CPC Class Codes: G06F 11/0757 by exceeding a time limit, i.e. time-out, e.g. watchdogs
• CPC Class Codes: G06F 11/076 by exceeding a count or rate limit, e.g. word- or bit count limit
• CPC Class Codes: G06F 11/0793 Remedial or corrective actions recovery from an exception in an instruction pipeline G06F9/3861; by retry G06F11/1402; for recovering from a failure of a protocol instance or entity H04L69/40
• CPC Class Codes: G06F 11/2094 Redundant storage or storage space G06F11/2056 takes precedence
• CPC Class Codes: G06F 12/0246 in block erasable memory, e.g. flash memory
• CPC Class Codes: G06F 2212/7204 Capacity control, e.g. partitioning, end-of-life degradation
• CPC Class Codes: G06F 2212/7211 Wear leveling

Abstract

Systems and methods are disclosed for monitoring the time it takes to perform a write operation, and based on the time it takes, a determination is made whether to retire a block that is a recipient of the write operation. The time duration of the write operation for a page or a combination of pages may indicate whether any block or blocks containing the page or combination of pages is experiencing a physical failure. That is, if the time duration of the write operation for a particular page exceeds time threshold, this may indicate that this page requires a larger number of program cycles than other pages. The longer programming cycle can be an indication of cell leakage or a failing block.

Claims

1. A method for selectively retiring a block in a non-volatile Nand flash memory, the method comprising:

writing data into at least one page of a block;

determining a time period, Tprogram, it takes for data to be programmed into each of the at least one page;

determining if the Tprogram time period falls within a lower bound and an upper bound of a Tprogram threshold; and

in response to determining that the Tprogram time period falls within the lower and upper bounds of the Tprogram threshold, determining whether to retire the block containing the at least one page based on at least one characteristic associated with the at least one page.

2. The method of claim 1, wherein the Tprogram threshold is set to identify a page that is potentially experiencing a physical failure.

3. The method of claim 1, the at least one page may be added to a data structure structure designed to keep track of pages exhibiting longer Tprogram time periods.

4. The method of claim 1, wherein if the Tprogram time period exceeds the upper bound, the block containing the at least one page having the Tprogram time that exceeds the upper bound is retired.

5. The method of claim 1, wherein determining the Tprogram time period comprises receiving feedback data from the nand flash memory.

6. A method for using timing data associated with a non-volatile memory, the method comprising:

obtaining timing data for at least one page in at least one block, the timing data associated with a time duration to perform a write operation;

applying criteria to the timing data, wherein the criteria comprises a lower time threshold and an upper time threshold; and

determining whether to retire the at least one block if the criteria falls within the lower and upper time thresholds.

7. The method of claim 6, wherein the timing data comprises a time duration to buffer data and a time duration to program data.

8. The method of claim 7, wherein applying criteria comprises determining if the time duration to program data exceeds the upper time threshold.

9. The method of claim 6, wherein obtaining timing data comprises obtaining the timing data for each programmed page in a block.

10. The method of claim 6, wherein obtaining timing data comprises obtaining the timing data for at least one page in each block of a superblock.