January 15th 2023

what’s NorFlash, NandFlash and eMMC ?

What is flash memory?



Ⅰ Types of flash memory

Ⅱ Embedded MMC(eMMC)

III Comparison of NOR flash,

1.1 NOR flash memory

2.1 eMMC architecture

Nand flash and eMMC

1.2 NAND flash memory

2.2 eMMC applications

3.1 Performance comparison

2.3 eMMC advantages

3.2 Capacity and cost

3.3 Physical form of storage

3.4 Reliability and durability

Types of flash memory

1.1 NOR flash

One of two non-volatile storage technologies is NOR flash memory. In 1988, Intel was the first to invent NOR flash memory, which outshined EPROM (Electrically Erasable Programmable Read-Only Memory) and EEPROM (Electrically Erasable Programmable Read-Only Memory) in the flash memory field. Then, in 1989, Toshiba released the NAND Flash structure, emphasizing cheaper cost per bit and higher performance, as well as the ability to be easily upgraded using a disk-like interface. NOR flash has a feature called XIP (execute in place). As a result, instead of reading code into the RAM system, applications can operate inside Flash. NOR has a high transmission efficiency and a cost-effective tiny capacity of 1-4mb, but its write and erase speeds are slow, which has a significant impact on its performance. NAND’s structure allows for exceptionally high cell density and high storage densities, as well as quick write and erase speeds. The challenge in using NAND is that flash management necessitates a unique interface. NOR is generally quicker than NAND for reads, and NAND is substantially faster for writes, which should be taken into account when designs are made.

It replaces old ROM chips by providing a complete address and data bus and allowing random access to any part of memory. ROM chips were generally employed at the time to hold code that was rarely updated, such as the BIOS of a computer or the firmware of a set-top box. NOR flash formed the foundation for early removable flash storage media and can endure 10,000 to 1,000,000 erase cycles. Compact flash was originally based on NOR flash, but was eventually switched to NAND storage due to its reduced cost.

1.2NAND flash

NAND Flash is a non-volatile storage technology that uses nonlinear macro mode internally to give a low-cost, high-performance option for solid-state massive memory. Toshiba developed it a year after NOR was released. Nand flash memory has a big capacity and a quick rewrite speed, making it ideal for storing vast amounts of data. NAND flash has a faster erase time and a smaller area per memory cell than NOR flash, allowing it to have a higher storage density and cheaper cost per bit. It has a ten-fold higher erase rate than NOR flash. While NAND flash’s I/O interface does not have random access to the external address bus, it must be read in blocks, and NAND flash blocks are often hundreds to thousands of bits in size.

NAND storage is not an effective alternative for ROM for loading programs since most microprocessors and microcontrollers require byte-level random access. NAND flash, in this sense, resembles a secondary storage device such as a CD or hard drive. Large storage devices, such as memory cards, benefit from NAND flash. Smart media was the first removable storage media made from NAND flash memory.

In the industry, NAND flash memory is frequently utilized in digital cameras, MP3 player memory cards, compressed U disks, and other embedded goods.

Ⅱ Embedded MMC(eMMC)

eMMC (embedded multi media card) is an embedded memory standard specification formulated by the MMC Association for such products as mobile phones and tablet PCs. eMMC integrates the controller into the device, provides a common interface, and controls flash memory, allowing handset manufacturers to concentrate on other aspects of the phone and accelerate time to market. eMMC, which is equivalent to a Nand flash+ master IC, has interface rates of up to 52 megabits per second and scalable performance. 1.8V or 3.3V can be used as the interface voltage. Their qualities are crucial to NAND suppliers that want to lower the size and cost of their lithography.

2.1 eMMC architecture

It comprises of a compact BGA package that houses an embedded storage solution with MMC interface, a flash memory device, and a host controller. eMMC provides rapid and scalable performance with interface rates of up to 52 megabits per second. 1.8v or 3.3v can be used as the interface voltage.

2.2 eMMC applications

eMMC is a high-capacity memory card used in consumer electronics. It has been used in some of the hottest products such as the Palm Pre, Amazon Kindle II, and Flip MinoHD, which are just a few of the hottest goods that entered into commercial production in 2011. To determine what type of memory these goods employ, iSuppli used its disassembly analysis business to disassemble them and discovered eMMC inside.

2.3 eMMC advantages

1) Lean design

The most prevalent local storage solution for mobile devices is eMMC. Its goal is to make mobile phone memory design easier. The technical aspects of different brands, such as Samsung, KingMax, Toshiba, Hynix, and Micron, must be changed to match the distinct products and technological qualities of the various brands. NAND Flash chips did not have a technical label in the past.

2)Fast update speed

Customers must rethink their mobile phones every time the NAND flash process changes, such as from 70nm to 50nm or from 40nm to 30nm. Every year, new semiconductor product technologies develop, and the speed of new phones is slowed by memory issues. As a result, as society progresses, the concept of an eMMC NAND flash control chip packaged in 1 MCP for storage and management will become more widespread.

3)Increase of running speed

The eMMC format was created to make it easier to use phone memory. It combines the NAND flash and control chips into a single MCP chip. Customers of mobile phones merely need to purchase eMMC chips and install them in new phones. They won’t have to deal with any other complicated NAND flash compatibility or maintenance issues.

III Comparison of NOR flash, Nand flash and eMMC

3.1 Performance comparison

Flash memory is a type of non-volatile electronic computer memory that can be electronically wiped and reprogrammed into blocks of memory cells. Write in any flash device can only be done in empty or erased cells. As a result, in most circumstances, erase must be done before write in the device. While NAND devices are simple to erase, NOR devices require that all bits in the target block be set to 0 before erase.

Since erase of NOR devices is performed in blocks of 64 to 128KB, the write/erase procedure takes 5 seconds. NAND chips, on the other hand, do erase in blocks of 8 to 32KB, which can take up to 4 milliseconds.

The performance gap between NOR and NAND is further widened by the difference in block size during erase. Multiple erase operations must be performed in the Nor-based cell for a given set of writes (particularly when updating small files), according to the statistics. As a result, when selecting a storage solution, designers must consider the following factors.

  1. The read speed of NOR is slightly faster than that of NAND.
  2. NAND has a significantly quicker write speed than NOR.
  3. The 4ms erase speed of NAND is substantially faster than the 5s of NOR.
  4. Most write actions necessitate a previous erase operation.
  5. The erase unit in NAND is smaller, and there are fewer erase circuits.

Furthermore, NAND’s actual application is far more complicated than that of NOR. You can either utilize NOR directly or run the code directly. However, NAND requires an I/O interface, which necessitates the installation of a driver. In fact, most operating systems currently support flash memory which is employed in NAND architectures. In addition, the Linux kernel provides NAND structures with Flash support.

Smartphones, digital tablets, multimedia players, PDAs, navigation systems, and digital cameras are all examples of high-performance portable consumer devices that utilise eMMC.

3.2 Capacity and cost

NAND flash cells are nearly half the size of NOR flash cells, and because of the simpler manufacturing process, the NAND structure can provide more capacity in a given die size, resulting in a price decrease.

With capacities ranging from 1 to 16MB, NOR flash memory dominates the flash memory market, whereas NAND flash memory is exclusively utilized for B-type devices with capacities ranging from 8 to 128MB, indicating that NOR is primarily used for code storage and storage media. NAND is ideal for data storage, with the CompactFlash, Secure Digital, PC Cards, and MMC memory card markets being dominated by NAND.

In a convenient embedded container, eMMC memory hides the intricacies of flash technology. As a result, chip designers will save time and money. Furthermore, because the embedded controller is integrated into the memory chip, no interface software for all types of NAND memory is required.

3.3 Physical form of storage

Data is stored in NAND flash memory cells in a bit pattern. In most cases, a cell can only store one bit. The byte (x8)/word (x16), which is the bit width of the NAND Device, is formed by connecting these cells to bit lines in 8 or 16 cells. These lines, in turn, create pages (there are other structures in NAND Flash). A page is the read and write data of NAND Flash, whereas a block is the erase data. This method can be used to create three different types of addresses.

  1. Column Address: the starting address of the register
  2. Page address
  3. Block address

eMMC refers to a package that includes both flash memory and a flash memory controller on a single silicon board. Its safe erase and trim capabilities, as well as high-priority interrupts, are suited for high-performance and security requirements.

3.4 Reliability and durability

Reliability should be considered when using flash media. For systems that require a long MTBF, flash is an ideal storage option. The maximum number of contacts per block of NAND flash is one million, while the maximum number of contacts per block of NOR flash is 100,000. A typical NAND block is eight times smaller than a NOR device, and each NAND memory block has fewer deletions in a given amount of time, in addition to the 10-to-1 block erase cycle advantage.

Flash drives also have better dynamic shock resistance than hard drives. Because of these characteristics, flash memory is commonly employed in mobile devices. Another advantage of flash memory is that it is extremely dependable when used in memory cards and can endure high pressures and extreme temperatures, even when submerged. Write of flash is typically much slower than read.

High priority interrupts and secure erase are two aspects of the eMMC v4.41 standard that improve performance, security, and reliability. Year after year, the eMMC application market grows.

Frequently Asked Questions about NOR flash, NAND flash and eMMC

1.What does NOR mean?

NOR flash memory is one of two forms of flash memory that are widely used. The other is NAND flash, which is more recent. Flash memory is a type of non-volatile computer memory that can be erased and rewritten electrically. The term “non-volatile” refers to the fact that the information contained on the chip does not require any power to maintain.

2.What is the use of NOR flash memory?

What exactly is NOR Flash? NOR flash is often used in applications that require writing and retrieving individual bytes of data, as well as random access and execute-in-place access techniques.

3.How to define NAND flash?

NAND flash is a non-volatile storage technology that stores data without the use of electricity. A common example is a cell phone, which uses NAND flash memory (also known as a memory chip) to store data files such as images, videos, and music on a microSD card.

4.How does NAND flash work?

NAND flash memory. NAND flash also uses floating-gate transistors, but they connect in a way that resembles a NAND gate: several transistors connect in series, and the bit line goes low only if all the word lines are pulled high (above the transistor VT).

5.The difference between NAND and NOR

The architecture and purpose of NOR and NAND flash differ. Code is stored and executed in NOR memory, which provides for quick random access to any position in the memory array. For data storage, NAND memory is employed.

6.How long can NAND flash be used?

About 10 years.
Most manufacturers claim that their flash memory devices have data retention lengths of around 10 years as a guideline, but, as with endurance, there are a variety of factors that influence the actual data retention times of the related storage devices.

7.What does eMMC mean?

Embedded Multimedia Card
eMMC stands for “Embedded Multimedia Card,” which is a product that includes flash memory and a flash controller on the same silicon die.

8.Which is better, eMMC or HDD?

Embedded Multimedia Cards, or eMMCs, are a type of flash storage that is less expensive and slower than solid state drives. eMMC is a type of flash memory that is often found in smartphones and other consumer electronics, but it is also found in desktop PCs. The performance of eMMC storage in normal use is in between that of HDDs and SSDs.

9.Is it possible to replace eMMC with an SSD?<

eMMC storage is not even considered a hard drive, and they’ll be soldered to the laptop board. It is not easily replaceable…. You can actually update your laptop with an internal hard drive or SSD if it has a free SATA port.

10.Is it possible to replace eMMC memory?

Unfortunately, because eMMC is soldered to the motherboard of the device, it cannot be upgraded. Although Windows 10 may be installed there, the 32GB of storage is a severe limitation.

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