8. NandFlash principle analysis

This section mainly introduces the knowledge related to NandFlash, first of all, the role, classification and access method of NandFlash.

1. Role analysis: In personal PCs, hard disks are used to store operating systems, data and other information. In the embedded field, NandFlash has hard disk function. So NandFlash is used to store information.

2. NandFlash classification:

SLC principle diagram:

MLC principle diagram:

From the above, we can see that the storage density of MLC is twice that of SLC. Here is the information comparison between the two:

Next is the access method:

1. Addressing method.

2. Address structure.

3. Signal pin.

1. Addressing method:

First look at the memory addressing diagram (ARM9):

The above is a schematic diagram of the memory, with address lines and data lines, both of which are connected to the CPU.

You can see that there are no data lines and address lines like memory in the schematic diagram of NandFlash. The memory here uses unified addressing, that is, the memory is included in the address space. NandFlash is outside the address space and uses independent addressing. NandFlash working diagram:

2. Address structure:

The basic composition of K9F2G08U0A-Nand Flash:

As can be seen above, a NandFlash device is divided into multiple blocks, each block is divided into multiple pages, and each page is divided into (2K+64) bytes. 2K is the main data area for storing data, and 64 bytes is the free data area for storing information such as checksums.

The row address is the Page number. To access a storage unit, you need to first know the Page number (column address). The column address is the offset in the Page, which can be used to locate the unit to be accessed.

3. Pin signal:

The remaining pins have signal information.