Defect logging in nonvolatile memory

摘要

A method of operating a nonvolatile memory block includes reading data from physical units in the block and determining individual error rates for data from the physical units. The error rate data is stored. This is repeated over multiple iterations and aggregated stored error rates are used to identify bad physical units in the block.

主权项

1. An apparatus comprising:
an individually erasable physical block of nonvolatile memory cells; a plurality of physical units in the individually erasable block; an error detection circuit configured to obtain individual error rates for data from the plurality of physical units; an error log configured to store the individual error rates for the data from the plurality of physical units; and a persistent error identification circuit configured to identify one or more physical units in the individually erasable physical block as bad and not for subsequent storage of user data while other physical units in the individually erasable physical block that are not identified as bad remain available for subsequent storage of user data, the the persistent error identification circuit configured to aggregate stored individual error rates from the error log over two or more write-erase cycles to identify the bad physical units.