SPI NOR FLASH Capacity Shortage on MCU! CS brand SD NAND Can Provide a Solution
*For the sake of understanding and to avoid the trouble of unit conversion, all capacity units mentioned below are in Bytes (8bit = 1Byte).
Introduction:
NOR FLASH is one of the two main non-volatile flash memory technologies in the market. Intel first developed NOR Flash technology in 1988 (although Toshiba's Fujio Masuoka was the first to develop it), which completely changed the dominance of EPROM and EEPROM at that time. Subsequently, in 1989, Toshiba introduced NAND Flash structure, emphasizing cost reduction per bit, higher performance, and the ability to easily upgrade like a disk through an interface. NOR Flash has the feature of execute-in-place (XIP), allowing applications to run directly from the flash memory without the need to load the code into system RAM. NOR has high transfer efficiency and cost-effectiveness for small capacities ranging from 1 to 4MB. However, its low write and erase speeds significantly affect its performance. NAND's structure provides extremely high cell density, enabling high storage capacity, and it also has fast write and erase speeds. The challenge with using NAND lies in the need for specialized system interfaces for flash management. Typically, NOR has slightly faster read speeds compared to NAND, while NAND has much faster write speeds than NOR. These factors should be considered in the design.
Main Content:
With the rise of the Internet of Things (IoT), the application of MCU has became increasingly widespread. In the past, most requirements could be fulfilled by using built-in EEPROM or external small-capacity NOR Flash. However, with technological advancements and increased application demands, MCU are now required to implement more functions, leading to larger data storage demand. For example, bigger system, storing audio, images (GUI), video buffers, protocol stacks, and more.
In general, when the capacity of NOR FLASH is insufficient, users can upgrade to a higher-capacity NOR FLASH to meet their demand. However, there is a particular situation to consider. Due to the relatively large unit structure of NOR, the cost-effectiveness decreases significantly once the capacity reaches a certain level. Considering production processes and the current market situation, 16MB acts as a turning point. The price of 32MB NOR FLASH, which is much higher than 16MB NOR FLASH and even more expensive than 128MB NAND FLASH. Moreover, the supply of 32MB NOR FLASH is not good, and even if users can accept its price, they may face difficulties in purchasing the product during mass production, and miss the optimal timing for selling the final product.
At this point, someone might say, "I already know all of this! I also want to use NAND Flash! But my MCU does not support NAND Flash! Do I have to change platforms and start development from scratch?"
No, things are different now. There is something called SD NAND that you can choose. It has the NAND architecture and uses the SD protocol, allowing it to be used with MCU that support SD 2.0 protocol. Normally, it is used in SPI mode, but if higher speed is required and there are enough IO ports, SD mode can be used. It includes built-in EDC/ECC, bad block management, and wear leveling functions. This means that users do not need to write additional drivers to manage NAND.
For more information about CS Brand SD NAND, please refer to the following article: Link: Introduction For CS SD NAND
Due to the use of NAND architecture in the storage units of SD NAND, it has the basic characteristics of NAND. SD NAND further optimizes these characteristics, greatly enhancing usability and application compatibility.
Let's take a look at the differences between NOR and NAND.
1. NOR Flash supports random access, enabling Execute In Place (XIP), whereas NAND Flash requires block-based reading and does not support XIP.
2. The theoretical read speeds of NAND FLASH are similar to NOR Flash, but actual performance may vary depending on the interface.
3. Both NOR and NAND require erasing before writing. NOR erases blocks of 64-128KB, taking approximately 5 seconds for a write/erase operation, while NAND erases blocks of 8-32KB, taking about 4 milliseconds for a write/erase operation.
4. NAND has a higher theoretical maximum erase count compared to NOR.
5. NOR has simpler driver requirements, whereas NAND FLASH requires specialized communication with the host through NAND FLASH Interface (NFI), resulting in more complex drivers.
6. Bit flipping occurs in all Flash devices, but the probability of bit flipping is higher in NAND. NAND Flash must use EDC/ECC (Error Correction Code) to mitigate this issue.
7. NAND's cell size is approximately half that of NOR, resulting in lower costs for NAND.
In conclusion： NOR and NAND have their own characteristics, along with different application scenarios and levels of difficulty. SD NAND retains the excellent features of NAND architecture while improving its shortcomings. The built-in controller manages NAND Flash independently, eliminating the need for external ECC handling and bad block management, and avoiding the complexities of the Memory Technology Device (MTD) layer. Users do not need to write driver code. These features make it possible for NOR users to upgrade to NAND.
CS brand offers capacities such as 128MB, 512MB, 4GB and 8GB, with options for both commercial and industrial-grade solutions. Users can choose according to their specific requirements.
128MB details：1Gb-128MB-SD NAND
Apart from SD NAND, there is an alternative upgrade option using TF (TransFlash) cards. However, the suitability of this solution depends on the specific application environment. For a comparison between SD NAND and TF cards, you can refer to the following article. We hope you can find the product that best suits your needs.
link：Differences between CS SD NAND and TF Card
If for some reasons, upgrading to SD NAND is temporarily not possible, you can also consider cost-effective NOR FLASH options. Currently, there are options available in capacities of 8MB (64Mbit) and 16MB (128Mbit). Interested individuals can visit the product details page for more information.
link: 8MB/64Mbit SPI NOR
If you have any questions, please contact us
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