Last written page searching

Abstract

An example method of the present disclosure includes, responsive to a loss of last written page information by a memory system, initiating a last written page search to determine last written page information of a memory device, where the last written page search is initiated via a command from a controller of the memory system to the memory device, responsive to receiving the command, performing the last written page search on the memory device, and providing the last written page information to the controller.

1 .- 20 . (canceled) 
     
     
         21 . A memory device, comprising:
 a plurality of memory units; and   an internal controller coupled to the plurality of memory units and configured to:
 receive a command associated with a power loss event; and 
 responsive to receiving the command, perform a last written page search to determine last written page information of the memory device; 
 wherein performing the last written page search comprises:
 commencing the last written page search by performing a word line search for determining a particular word line using a binary search of word lines for a particular one of a group of sub-blocks; wherein the binary search of the word lines includes setting a start pointer to a first word line and an end pointer to a last word line and performing an erase check of the particular one of the group of sub-blocks; and 
 responsive to determining the particular word line corresponding to a last written page of a block, performing a subsequent binary search of sub-blocks coupled to the particular word line to determine a particular sub-block in which the last written page of the block is located. 
 
   
     
     
         22 . The memory device of  claim 21 , wherein the internal controller stores page map information. 
     
     
         23 . The memory device of  claim 21 , wherein data stored in the last written page comprises information which indicates whether memory cells of the last written page are fully programmed. 
     
     
         24 . The memory device of  claim 21 , wherein the internal controller is configured to provide the determined last written page information of the memory device to a system controller external to the memory device. 
     
     
         25 . The memory device of  claim 21 , wherein the last written page is configured to store status information. 
     
     
         26 . The memory device of  claim 21 , wherein the last written page information is configured to be read from the memory device via an external controller. 
     
     
         27 . The memory device of  claim 21 , wherein the memory device is commonly coupled to a number of additional memory devices via a bus. 
     
     
         28 . The memory device of  claim 21 , wherein the plurality of memory units comprise respective memory dice. 
     
     
         29 . The memory device of  claim 28 , wherein the respective memory dice comprise NAND memory arrays. 
     
     
         30 . An apparatus, comprising:
 a system controller;   a plurality of memory devices coupled to the system controller, wherein at least one of the plurality of memory devices comprises:
 a block of memory cells; and 
 an internal controller coupled to the block and configured to, responsive to receiving a command associated with a loss of last written page information, determine a last written page of the block by:
 commencing a last written page search by performing a word line search for determining a particular word line using a binary search of word lines for a particular one of a plurality of sub-blocks of the block; 
 wherein the binary search of the word lines includes setting a start pointer to a first word line and an end pointer to a last word line and performing an erased page check of the particular one of the plurality of sub-blocks; and 
 responsive to determining the particular word line corresponding to a last written page of a block, performing a subsequent binary search of sub-blocks coupled to the particular word line to determine a particular sub-block in which the last written page of the block is located. 
 
   
     
     
         31 . The apparatus of  claim 30 , wherein each sub-block of the plurality of sub-blocks comprises physical pages respectively coupled to different ones of a plurality of word lines; 
     
     
         32 . The apparatus of  claim 30 , wherein the internal controller is configured to provide the determined last written page information to the system controller. 
     
     
         33 . The apparatus of  claim 30 , wherein the system controller is configured to read the determined last written page information from the at least one memory device. 
     
     
         34 . The apparatus of  claim 30 , wherein data stored in the last written page comprises information which indicates whether memory cells of the last written page are fully programmed. 
     
     
         35 . The apparatus of  claim 30 , wherein the erased page check comprises reading an erase status from the particular one of the plurality of sub-blocks. 
     
     
         36 . The apparatus of  claim 30 , wherein the last written page information includes a feature address. 
     
     
         37 . The apparatus of  claim 30 , wherein the at least one memory device maintains a page map that provides a physical page address for each of a plurality of combinations of an access line address and a sub-block address. 
     
     
         38 . The apparatus of  claim 30 , wherein the command is provided to the at least one memory device responsive to an asynchronous power loss event. 
     
     
         39 . A system, comprising:
 a controller comprising a host interface and a memory device interface; and   a plurality of memory devices coupled to the controller via a bus, wherein each one of the plurality of memory devices comprises an internal controller configured to, responsive to a loss of last written page information by the system, initiate a last written page search to determine last written page information of the plurality of memory devices;   wherein the last written page search comprises:
 performing a word line search for determining a particular word line using a binary search of word lines for a particular one of a group of sub-blocks; 
 wherein the binary search of the word lines includes setting a start pointer to a first word line and an end pointer to a last word line and performing an erase check of the particular one of the group of sub-blocks; and 
 responsive to determining the particular word line corresponding to a last written page of a block, performing a subsequent binary search of sub-blocks coupled to the particular word line to determine a particular sub-block in which the last written page of the block is located. 
   
     
     
         40 . The system of  claim 39 , wherein the last written page search is performed concurrently by the plurality of memory devices.