Initialization scheme during dual programming of a memory system

• US 9,582,358 B2
• Filed: 04/30/2015
• Issued: 02/28/2017
• Est. Priority Date: 09/30/2014
• Status: Active Grant

• Current Assignee: SanDisk Technologies LLC (Western Digital Corporation)
• Original Assignee: SanDisk Technologies LLC (Western Digital Corporation)
• Inventors: Agarwal, Dinesh, Sivasankaran, Vijay
• Primary Examiner(s): Rizk, Sam
• Application Number:
  US14/700,543
• Publication Number:
  US 20160092302A1
• Time in Patent Office: 670 Days
• US Class Current: 1/1
• CPC Class Codes: G06F 11/1068 in sector programmable memories, e.g. flash disk G06F11/1072 takes precedence
• CPC Class Codes: G06F 3/0616 in relation to life time, e.g. increasing Mean Time Between Failures [MTBF]
• CPC Class Codes: G06F 3/0619 in relation to data integrity, e.g. data losses, bit errors
• CPC Class Codes: G06F 3/064 Management of blocks
• CPC Class Codes: G06F 3/0679 Non-volatile semiconductor memory device, e.g. flash memory, one time programmable memory [OTP]
• CPC Class Codes: G11C 29/52 Protection of memory contents; Detection of errors in memory contents
• CPC Class Codes: G11C 7/20 Memory cell initialisation circuits, e.g. when powering up or down, memory clear, latent image memory

Abstract

A memory system or flash memory device may include mechanism for handling power loss with a dual programming architecture. The state of primary and secondary blocks may be reconstructed to a state immediately preceding a power loss. The reconstruction may include comparing error correction code (ECC) headers of blocks to recreate a block exchange with fewer control updates. The comparison can be used to identify a primary and secondary block. The header may identify a particular stream, identify a free block, identify a release block, and other information.

Claims

1. A method comprising:

establishing, for a memory system, a primary update meta-block and a secondary update meta-block for dual programming in one or more streams;

cycling the primary update meta-block and the secondary update meta-block by utilizing a free block list;

storing a stream index and a free block list index in an error correction code (ECC) page header of pages of both the primary update meta-block and the secondary update meta-block; and

determining, upon a power cycle in the memory system, the primary update meta-block and the secondary update meta-block for the one or more streams utilizing a comparison of the ECC page header.

2. The method of claim 1 wherein the cycling comprising:

converting the secondary update meta-block into the primary update meta-block; and

converting a block from the free block list into the secondary update meta-block.

3. The method of claim 1 wherein each of the streams includes its own primary update meta-block and a secondary update meta-block.

4. The method of claim 1 wherein the stream index comprises an identification of one stream from the one or more streams and the free block list index comprises an identification of a block from the free block list that is cycled.

5. The method of claim 1 wherein the primary update meta-block is from a first di and the secondary update block is from a second di.

6. The method of claim 4 wherein the block that is cycled becomes the secondary update meta-block.

7. The method of claim 1 wherein the dual programming comprises:

programming, from a host write command, data to both the primary update meta-block and the secondary update meta-block;

checking for errors from the programming of the primary update meta-block;

committing the host write command from the primary update meta-block when there are no errors or failures with the primary update meta-block; and

committing the host write command from the secondary update meta-block when there are errors or failures with the primary update meta-block.

8. The method of claim 7 wherein cycling comprises:

closing the primary update meta-block;

selecting a free block from the free block list as the secondary update meta-block; and

utilizing the secondary update meta-block as the primary update meta-block for a subsequent host write command.

9. The method of claim 7 wherein the checking for errors comprises enhanced post-write-read error management (EPWR).

10. The method of claim 7 wherein the errors or failures comprises one or more uncorrectable error codes (UECC).

11. The method of claim 1 wherein the recreating further comprises:

identifying a stream to recreate for the primary update meta-block and the secondary update meta-block with the stream index;

identifying a next free block that is to be cycled before the power cycle with the free block list index;

cycling through the identified stream; and

comparing the ECC page headers for each block that is cycled until the ECC page headers match.

12. The method of claim 1 wherein the ECC header further comprises a release meta-block, wherein the release meta-block is a next block added to the free block list.

13. A method in a dual programming memory system comprising:

replaying a block exchange to identify a primary block and a secondary block immediately before a power cycle by starting with an initial primary block and an initial secondary block; and

comparing an error correction code (ECC) page header for each of the blocks during the replaying, wherein the primary block and the secondary block are identified when the ECC page headers match.

14. The method of claim 13 wherein the block exchange comprises:

converting the secondary block into the primary block;

converting a block from a free block list into the secondary block.

15. The method of claim 14 wherein the ECC page header includes a stream index and a free block list index, wherein the stream index comprises an identification of one stream from a plurality of streams programmed, and further wherein the free block list index comprises an identification of a block from the free block list that is part of the block exchange.

16. The method of claim 15 wherein the ECC page header further comprises a release meta-block, wherein the release meta-block is a next block added to the free block list.

17. A memory initialization method in a dual programming scheme comprising:

utilizing, for the dual programming scheme, a primary update block and a secondary update block in one or more streams;

cycling the primary update block and the secondary update block by utilizing a free block list to use a free block from the free block list as the secondary update block;

storing initialization information in an error correction code (ECC) page header of the free blocks from the free block list; and

initializing, upon a power loss, the primary update block and the secondary update block using the initialization information by comparing ECC page headers of the primary update block and the secondary update block as blocks are cycled.

18. The method of claim 17 wherein the initialization information comprises a stream index, a free block list index, and a release meta-block, wherein the stream index comprises an identification of one stream from a plurality of streams programmed, further wherein the free block list index comprises an identification of a block from the free block list that is cycled to the secondary update block, and further wherein the release meta-block is a next block added to the free block list.

19. The method of claim 18 wherein the initializing comprises:

identifying a stream to cycle for the primary update block and the secondary update block with the stream index;

identifying a next free block that is to be cycled before the power loss with the free block list index;

cycling through the identified stream; and

comparing the ECC page headers for each block that is cycled until the ECC page headers match.

20. The method of claim 17 wherein the dual programming scheme comprises:

programming, from a host write command, data to both the primary update block and the secondary update block;

checking for errors from the programming of the primary update block;

committing the host write command from the primary update block when there are no errors or failures with the primary update block; and

committing the host write command from the secondary update block when there are errors or failures with the primary update block.