Software-Enabled Flash™ (SEF) Unit

A SEF Unit is a set of dies and the associated control logic and (optional) DRAM. The dies are grouped by user-defined rectangular regions to form a many-to-one mapping of dies to a virtual device. A virtual device represents physical isolation with the number of virtual devices limited by the number of dies in the SEF Unit. Figure 6.1 shows an example of three virtual devices overlaid on an 8 x 4 SEF Unit with eight dies left unallocated.

Figure 6.1: SEF Unit Geometry

As shown in the figure 6.2, a die is a set of blocks. The blocks are the erase unit for a SEF Unit and consist of a set of pages. A page spans the die planes and is the programing unit. A plane is made up of atomic data units (ADUs). An ADU is the read/write unit holding both user data and metadata. Metadata consists of a user-defined tag data (UA) and a SEF-unit-created monotonically increasing serial number (SN).

Figure 6.2: Die Geometry