1. What is Flash?
2. What is NOR Flash?
3. How does NOR Flash?
4. Types of NOR Flash Memory
5. What is NAND Flash?
6. How does NAND Flash?
7. Types of NAND Flash Memory
8. NOR Flash vs. NAND Flash Features
9. The comparison between NAND Flash and NOR Flash
10. Conclusion of NAND Flash vs NOR Flash
With the advantages of NVRAM (NVRAM: Non-Volatile Random Access Memory), Flash combines the qualities of ROM and RAM. It has the ability to be electronically erasable and programmable (EEPROM), as well as the ability to read data quickly. In the past, embedded systems have used ROM (EPROM) as their storage device. With the advent of Flash, ROM (EPROM) has been completely replaced in embedded systems like used in Embedded IC. Flash can now be used as a hard drive (USB flash drive, solid state drive), as well as a storage bootloader for operating systems and program code. NOR Flash and NAND Flash are the two main types of flash memory, each of which having distinct benefits and disadvantages. The programming technologies of FPGA include Anti-fuse, SRAM, and EEPROM/Flash, while With the aid of CMOS EPROM, EEPROM, flash memory, and SRAM programming technologies, CPLD creates programmable logic devices that are very dense, swift, and energy-efficient. Flash can be divided into NAND Flash and NOR Flash.
In 1988, Intel invented NOR flash technology, which fundamentally altered the way EPROM and EEPROM were used. The reading of NOR flash is the same as that of regular SDRAM, i.e., it can be read and written randomly based on the address. Additionally, the user can run the code put in NOR FLASH directly, which can lower the cost of SRAM by reducing its capacity. It is mostly used to store programs, operating systems, and other crucial information due to its quick reading speed.
The FGMOS (Floating Gate Metal Oxide Semiconductor Field Effect Transistors) is the fundamental component of NOR flash memory. The Floating Gate is an area found in every transistor. The electrons contained within this region can either be trapped or released. The transistor is turned on, trapping these electrons. Each transistor is referred to as a memory cell since it can represent either 0 or 1.
In this particular type of NOR Flash, a parallel address bus is used by the memory controller to address the memory. Either an 8-bit bus or a 16-bit bus can be used for the parallel NOR. The Parallel NOR Memory with extra storage space can be addressed using a 16-bit address bus.
Parallel NOR SPI NOR—the acronym for "Serial Peripheral Interface"—is another name for flash. Pages and sectors are present, with sectors being larger. When data is being written on the pages of memory, a sector is a block of memory whose entire contents can be erased at once.
Toshiba released the NAND flash structure in 1989, highlighting its reduced cost per bit, faster performance, and simple upgradeability via a disk-like interface. The cost of producing Flash utilizing NAND Flash is lower because it does not use the random read technology of memory; instead, it reads in the form of individual chunks, typically 512 bytes at a time. In order to run the starting code, many development boards utilize a small NOR Flash in addition to NAND Flash because users cannot run the code directly on NAND Flash.
NAND Millions of MOSFET-based charge trap memory cells are used in flash memory. The nanotechnology used to generate these cells. Each Charge Trap Flash Memory (CTF) cell has the ability to either trap or release electrons. As a result, in the past, each cell could only represent one bit, either 0 or 1.
The three functional components of CTF are the Gate, the Channel, and the Charge Trap. These are all separated using a dielectric substance. Because of its ability to store or release the electrons it contains, the component is known as a charge trap. The cell symbolizes 1 if there are no trapped electrons, and 0 otherwise. More values can be stored in a single current CFT than in earlier ones. To do this, the Charge Trap component stores various charge levels. For instance, we require 8 different charges or voltages to represent 8 different values.
Single-level cells are referred to as SLCs. Due to the fact that each cell can only represent one binary digit (bit), this form of NAND Flash is outdated.
Triple-Level Cell is referred to as TLC. Since each cell houses three bits of memory, as implied by the name, more data can be stored in the same amount of space. Enterprise and consumer level businesses are the main users of TLC drives.
In a multi-level cell, two bits can be represented. Because Write Cycles and Ensure occur two times more frequently in these cells than in SLCs, they are less durable than SLCs.
NOR Flash Features:
NAND Flash Features:
There are enough address lines in the NOR Flash design to map the entire memory range. This is perfect for code execution since it offers random access and quick read speeds. 100% known good bits for the duration of the part is another benefit. The disadvantages of larger cells include slower write and erase speeds and a greater cost per bit.
In contrast to NOR Flash, NAND Flash features substantially smaller cells and faster write and erase speeds. The I/O mapped type or indirect interface, which is more complex and does not support random access, as well as the slower read speed, are drawbacks. It is significant to note that, in contrast to code execution directly from NOR Flash, code execution from NAND Flash is accomplished by shadowing the contents to a RAM. Bad blocks are yet another significant drawback. Error-correcting code (ECC) functionality is required within the device since NAND Flash typically has 98% good bits when shipped with additional bit failure over the part's life.
Data retention is another facet of dependability where NOR Flash once again excels. S70GL02GT Data retention for up to 1K Program/Erase Cycles on NOR Flash is 20 years. Data retention for S34ML04G2 NAND Flash is typically 10 years.
The quantity of program and erase cycles used to be a significant factor. This is due to the fact that NOR Flash memory used to provide 10 times as many program and erase cycles as NAND Flash memories. This is no longer true due to technology improvements, as both memories may now be compared. As an illustration, the S34ML04G2 NAND and S70GL02GT NOR both support 100,000 program-erase cycles. However, each operation only erases a smaller portion of the storage space because NAND Flash uses smaller blocks. Compared to NOR Flash, this leads in a longer overall life span.
Any memory device must take data dependability into consideration. Flash memory are susceptible to a condition known as bit-flipping, in which some bits can become reversed. Compared to NOR Flash, this phenomena occurs more frequently with NAND Flash. Due to concerns about yield, NAND Flashes are sold with defective blocks dispersed randomly throughout. Over the course of NAND Flash's lifetime, more memory cells degrade as erase and program cycles are performed. Therefore, NAND Flash must have the capacity to handle bad blocks. NOR Flash, on the other hand, has zero bad blocks when it is shipped and has a very low bad block accumulation during the course of the memory's lifespan. Thus, NOR Flash has an edge over NAND Flash in terms of the dependability of data saved.
Because NAND Flash memories have a lower cost per bit than NOR Flash, they can be found in considerably higher densities. NAND Flash memory normally ranges from 1GB to 16GB in size. The density of NOR Flash memory ranges from 64Mb to 2Gb. NAND Flash is utilized primarily for data storage applications due to its increased density.
When powered on for the first time, NOR Flash memories often require higher current than NAND Flash. However, NOR Flash has a significantly lower standby current than NAND Flash. Both Flash memory have comparable instantaneous active power. Thus, the length of time that memory is active determines the active power. While NAND Flash uses significantly less power when performing erase, write, and sequential read operations, NOR Flash has an advantage when it comes to random reads.
Conclusion of NAND Flash vs NOR Flash
In general, NOR Flash memory is a great option for programs that need a small amount of storage, quick random access, and highly reliable data, like programs that execute code. For its part, NAND Flash excels in applications like data storage where a larger memory capacity and quicker write and erase operations are necessary. Compared with NOR Flash, NAND Flash has better write performance and lower cost in large capacity. Currently, most of the Flash Memory used in cell phones, tablet PCs, SD cards, SSDs and other devices are NAND Flash.