Scheduling of housekeeping operations in flash memory systems

Abstract

A re-programmable non-volatile memory system, such as a flash EEPROM system, having its memory cells grouped into blocks of cells that are simultaneously erasable is operated to perform memory system housekeeping operations in the foreground during execution of a host command, wherein the housekeeping operations are unrelated to execution of the host command. Both one or more such housekeeping operations and execution of the host command are performed within a time budget established for executing that particular command. One such command is to write data being received to the memory. One such housekeeping operation is to level out the wear of the individual blocks that accumulates through repetitive erasing and re-programming.

Description

technical field [0001] This disclosure relates generally to the operation of non-volatile flash memory systems, and more particularly to techniques for implementing housekeeping operations such as wear leveling in such memory systems. All patents, patent applications, papers, and other publications referenced herein are hereby incorporated by reference in their entirety for all purposes. Background technique [0002] There are many commercially successful non-volatile memory products in use today, especially in the form of small form factor removable cards or embedded modules that use flash EEPROM formed on one or more integrated circuit chips (Electrically Erasable Programmable Read-Only Memory) cell array. A memory controller, usually but not necessarily on a separate integrated circuit chip, is included in a memory system to interface with a host to which the system is connected, and to control the operation of the memory array within the card. Such controllers typicall...

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Problems solved by technology

The specific usage of the host can also cause a few logical blocks to be rewritten with user data more frequently than others

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