Thank you for being part of the FixData community! This is our last issue of 2023, find topics related to NAND memory such as page allocations.

• NAND memory structure (Crystal)

• Removing NAND memory from a USB flash drive

• Single plane page mapping

• Testimony

• Premium content: Multiplan page allocation

NAND memory structure (Crystal)

NAND memory has an architecture that is essential for data storage. The most important element inside a NAND memory chip is a crystal, where the crystal has different components, which helps the memory to store information.

Among the components found in NAND memory crystals are the following:

• Peripheral devices: provide I/O operations (input and output), page decoding and manage the overall communication between the NAND crystal and the memory controller.

• Page buffer: this component helps maintain data that is temporary. 

• Plane: the plane is the component where the data entered by the user is written to be stored.

A NAND memory crystal can have one, two or up to four planes for data storage.

The controller is in charge of deciding in which way the data will be stored in the NAND memory crystals, it can write the data in two ways:

• Single-plane page allocation: this consists of writing the data in a sequential page manner to a physical block of a plane.

• Multi-plane page allocation: this process consists of writing parallel pages to the physical blocks of each plane (similar to RAID 0).

Removing NAND memory from a USB flash drive

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Single plane page allocation

As seen in the previous article, the controllers are responsible for determining how the process of writing data to the planes of the NAND memory crystal will be. One of these processes is the page allocation in a single plane. To better understand this method of writing information, it is necessary to remember how a NAND memory crystal is structured. A NAND memory crystal is structured as follows to store data:

1. Planes

2. Blocks

3. Pages

4. Cells

First, we have the planes. In its interior, several blocks are stored, where each block contains the pages. These, in turn, are structured by cells that are transistors that store the information at the bit level. Now that we know how the structure of the planes is conformed, we will continue with the way in which the controller writes the data when it works by assigning pages in a single plane.

When this method is used for structuring the information, the controller assigns the data pages sequentially in each physical block. As we can see in Image 1.0, we can see that in plane 0 and in plane 1, blocks 1 and block n+2, the arrangement of the pages is sequential, having page 0 to page n+1. This continues until reaching the maximum supported number of pages for the block, which is determined by the controller.

When assigning pages to a single plane, a data pattern is applied, as previously mentioned. The pages are stored sequentially, as shown in Image 2.0. Two blocks of data are shown, with block 1 having a pattern for storing data and block 2 having a different pattern for arranging the data.

Testimony

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