Flash is non-volatile memory, which is referred to as SDRAM and other memories. That is, after the memory is powered off, the internal data can still be saved. Flash is divided into Nand, Nor Flash and AG-AND Flash according to technical methods, and upgraded. But after more than ten years, there are still quite a few hardware engineers who cannot distinguish between NOR and NAND flash. In most cases, flash memory is only used to store a small amount of code. At this time, NOR flash memory is more suitable. NAND is the ideal solution for high data storage density.
Nor Flash is often used to store programs. When the MP3 chip was not mature at first, Nor Flash was used, such as ATJ2075 and SunplusSPCA7530. At present, this kind of Flash has not been used much, and only a few readers can see it in MP3 and digital photo frames. Because there is no memory in this SD card-supporting product, the ROM in the chip is not enough to store the program, so it needs to be used Nor Flash storage program.
In addition, AG-AND Flash is a technology of Japan's Renesas. The yield rate is not very high, and the effective capacity is relatively low. Flash from the original factory has a capacity of 88%, 92%, 96%, 96% can be used in MP3 products, while the other two can only be used in U disk and SD card products. I personally think its performance is relatively poor, try not to use it. Now Renesas has launched the ranks of Flash manufacturers, and AG-AND technology has also been transferred to Taiwan Powerchip to continue production.
There are also several types of Nand Flash, which are divided into three types, such as SLC, MCL, and MirrorBit. SLC is the abbreviation of Single Level Cell, which means that there is only 1 bit of data in each memory cell. MLC is Multi-Level-Cell, which means that the technology allows 2-bit data to be stored in one memory cell. MirrorBit has only 4 bits of data in each storage unit.
It can be imagined that the technology storage of SLC is relatively stable, and the technology of SLC is also the most mature. However, MLC can have 2bit data in one unit. The LC price is much lower than SLC. Under normal circumstances, the price of MLC and SLC with the same capacity is 30% to 40% lower than SLC, and some are even lower.
1. Look at the model of Flash: distinguish them according to the naming rules of Flash.
2. Format and see if it is stable:
Currently, black and white films are also popular in the market. These are the types of Downgrade Flash. Due to the improvement of Flash process and capacity, the internal composition is becoming more and more complicated. When the new process is launched, the product yield is not necessarily ideal. Some of the bad flashes are insufficient capacity, some are not able to meet the life expectancy, and some are failing the test. These flashes that do not meet the factory requirements are called Downgrade Flash . Some Downgrade Flash are brought to the market by manufacturers. For example, Spectech is Micron's Downgrade Flash. The other part is eliminated as waste products, but driven by profits, these waste products will also be bought into the market at low prices. Some manufacturers use various scanning tools (Soting Board) to check which ones can be used. These manufacturers purchase Flash to recycle by jins. At least dozens of Soting Boards are scanned together, so thousands of Soting Boards are scanned together, with a production capacity of hundreds of K per day. Most Downgrade Flash is made into SD card, a few are used for U disk, and very few manufacturers are used to produce MP3. Downgrade Flash is mostly dealt with by reducing capacity. However, no matter how to deal with it, there are still hidden problems. But due to the low price, the market for Downgrade Flash is growing further.