NAND Flash Memory Organization and Operations

Implementing Write Compression in Flash Memory Using Zeckendorf Two-Round Rewriting Codes

“…The flash memory in an SSD is physically organized into a hierarchy of progressively larger units of storage according to the structural relationships between the cells therein. Flash memory cells are arranged, in order of increasing units of size, as follows: a group of cells connected by a common word line constitutes a page; a group of pages embedded in a common substrate constitutes a block; groups of blocks which share an independent set of accessing hardware are known as planes; and one or more planes connected to a single memory controller, which is responsible for interpreting and executing memory commands [7], [8]. Pages and blocks, in particular, are of special significance to the operation of the SSD due to the way cells are structured in these organizational units.…”

“…For a memory with some preferred initial state or value, the processes of altering and restoring this value to the cells of such a memory are known respectively as programming and erasing; in an SSD, programming a cell thus sets its value to 0 while erasing the cell returns its value to 1. Many memories, including magnetic storage devices, can be programmed and erased symmetrically, meaning that programming and erasing are roughly equivalent processes, only differing in the value they assign to a memory's cells [8]. This allows such memories to rewrite previously programmed memory locations in-place, directly programming and erasing cells as necessary without any additional steps.…”